super tuesday. also tonight, elizabeth palmer takes us inside syria at a turning point in the civil war. >> reporter: there is certainly no cease-fire here at the moment, and there's not going to be any time soon. >> pelley: daylight reveals the destruction done by a night ofor violent storms. and will this idea take off? plans for a wide body aircraftde for wide bodies. >> at the end of the day, it's all about making money.ng captioning sponsored by cbs this is the "cbs evening news" with scott pelley. >> pelley: this is our western edition. tonight, the five republican presidential candidates are holding their final debate before super tuesday, the 12 primaries and caucuses that could be the turning point. for some it is a fight for survival, but for dominant donald trump, he is expected to draw most of the fire tonight,

become an issue. major garrett is in the debate city of houston. >> reporter: scott, republicans here all agree-- tonight could be one of the last chances to slow donald trump's momentum before key contests in his republican rivals' home state. a new poll here in texas shows ted cruz ahead, and john kasich has been leading in ohio. but another poll put marco rubio well behind trump in his home state of florida. today, trump focused on a different republican candidate, one from four years ago. the feud between mitt romney and donald trump started yesterday when romney repeated his call for trump to release his tax returns. trump then took to twitter to call romney one of the worstdida g.o.p. candidates ever and a dope. trump also tweeted a picture ofg himself signing what he said was a recent tax return. the caption, "isn't this?" ridiculous?"e ta the tax issue bedeviled romneyai in the 2012 campaign after

reid made a similar claim to now what romney is now saying about trump. >> the word's out that he hasn't paid any taxes for 10 years. let him prove that he has paid taxes, because he hasn't. >> reporter: the accusation was later debunked.pa for his part, trump has boasted tax he tries to keep his tax bill low. >> i fight like hell not to paypa taxes. i hate the way the government spends my money. >> reporter: and he noted on twitter that, "tax returns havee' zero to do with someone's net worth." romney's response, "me thinksld the donald doth protest too much." trump's g.o.p. rivals marco rubio and ted cruz have both pledged to release their returns. >> they're just not very exotic, but we will release them, sure. >> i haven't made enough money that my tax returns are not that interesting. >> reporter: donald trump is ong. a three-state winning streak and won 60% of the delegates awarded so far. tuesday presents the biggest haul of all-- 595 delegates,ha just under half of the amount required to secure the republican nomination.

tonight. major, thank you very much. the next democratic debate-- i should say primary, is saturday in south carolina. here's nancy cordes. >> we could just turn this into a revival. >> reporter: hillary clinton'sa. inner preacher came out today as she courted black crowds in south carolina low country. >> i think we need more singing, don't you? i i sing because i'm happy. i sing because i'm free! >> reporter: in michigan, bernie sanders was focused on minorities, too, meeting with residents in water-stricken flint. >> people were coming saying, "this water is brown. we're getting rashes," and theyy continued to ignore it. >> reporter: neither candidatee- can win in the delegate-rich super tuesday states without minority support.00 in 2008, african americans alone made up half of the democratic electorate in alabama and georgia, and nearly a third in and virginia and tennessee. 32% of democratic voters in

>> when you have people like trump saying that mexicans are rapists or criminals, that is an outrage.or >> reporter: a new national polls finds clinton leading sanders among hispanic voters by a. margin of two to one. she has a similar edge with african americans though herim husband's crime bill has been a sticking point for some. two black lives matters protesters interrupted a clinton fund-raiser in charleston last night. >> reporter: the protesters were escorted out, and clinton later said she was sorry for some of th the terms she used in the 90s, including the use of the phrase "super predators." she was using the term to describe violent young gang members, but now, 20 years later, says it was a poor choice of words. both clinton and sanders want to reform the way drug crimes, in particular, are handled, scott, because they say too many young blacks and latinos are ending up

thank you, nance. a study out today confirms the methane leak that forced thousands from their homes in porter ranch, california was the largest in u.s. history. over four months, the ruptured well spewed more than 100,000 tons of methane-- almost as much pollution as 600,000 cars put out in a year. in syria, u.s.-backed rebels are on the run. the forces of the assad dictatorship are advancing for the first time in years, because of russian air support and iranian troops. it's rare for a reporter to get into syria, but today our elizabeth palmer covered the dictatorship's advance through >> reporter: this used to be a neighborhood. now it's a battlefield.e where the syrian army says it's got the enemy on the run. there's just been an air strike behind me.

center of damascus, and the syrian army is trying to clear this suburb of opposition fighters. there is certainly no cease-fire here at the moment and there's not going to be at any time soon.yria solmer, one of the syrian soldiers, take us to see the buildings half a mile away where he says the rebels are now hiding.pt overhead, we can hear the helicopters scouting their target. then... ( explosion ) what are they hitting, solmer? "they're terrorists," he says. those are barrel bombs? barrel bombs are basically canisters filled with explosives rolled out of a chopper. they're cheap but horribly inaccurate. and are there any civilians left over there? "no, no," he says "only fighters," but there are' fighters' families, too, cowering under the attacks. nearby, we enter tunnels the

fighters with the al qaeda-t linked al-nusra front where they hid and fought for years. general youssuf, the man in charge, leads the way through ruins he now controls. you're still using air strikes in the suburbs in order to fight nusra? "yes," he says, "because they're dangerous for syria and the world so we're justified in using any weapons that are legal." but that means that when this over-stretched and undertrained army does gain ground, itslo victories look like nothing more than few blocks of rubble. but the truth is, scott, that by now, all sides in this war are completely exhausted, anda unlikely as it sounds, just a couple of suburbs over, the army has actually reached a mini truce with the rebels to allow food and supplies to reach civilians. >> pelley: elizabeth palmer with rare firsthand reporting inside

elizabeth, thank you. there is breaking news tonight about a shooting at a factory in hesston, kansas. that's north of wichita. we'll go now for the latest details. >> reporter: i'm kristine johnson. local police officials confirm at least four people have been killed and as many as 20 injured in a work-related shooting at excel industries in hesston, kansas. that area is located north of wichita. the shooter, who was identified as cedric ford by eyewitnesses and also our local affiliate, was pronounced dead. the suspect was an employee at excel industries, but it is unclear if he was a current or former employee. now, at the request of local authorities, the f.b.i. is en route to provide assistance in this investigation. no other information has been released, including the names of the victims. we do know that governor sam

this, "please send your thoughts and prayers to the people of hesston tonight." tune in to your local stations for more information on this developing story. we now return you to scott pelley.ev >> pelley: tornadoes in several states yesterday killed at least four people, including three in waverly, virginia, where we find chip reid tonight. >> man, it's an experience, man. you got to experience it to talk about it.nt >> reporter: vincent donald was about to sit down right here to watch tv when the tornado slammed into his mobile home, sheering off the roof and the wall. do you feel lucky to be alive? >> i'm not lucky. i'm blessed. >> reporter: but the tornado tore his neighbor's mobile homen from its foundation and sent itro sailing across a highway. a two-year-old boy, his father, and another man died. their bodies and other debris were found 300 yards away. somehow, the boy's mother survived with serious injuries.

a 78-year-old man died and 100 buildings were damaged after aight funnel cloud left an eight-mile path of destruction. at least three tornadoes were reported in north carolina.m in oxford, parts of this farmevel were leveled. in pennsylvania, a tornado ripped through amish country, hitting structures in narvon. a torrential downpour lead to flash flooding in and around washington, d.c. and left one major road flooded for the morning commute. in the new york area, a gust of wind sent this truck airborne. and, scott, take a look at this. off queens, new york, 12-foot waves capsized a coast guard boat as it was trying to rescue fishermen on another vessel that had run aground. and back here in waverly,a virginia, you're looking at apl photograph of a-plus tires before the tornado.k now you're looking at a-plus tires after the tornado. this was the garage door. that up thereris the metal that was once the roof.

what happens when a tornado meets a building made of sheet metal. >> pelley: and we want to point out, no one was injured in the coast guard incident today. chip, thanks very much. the world's appetite for portable electronics has triggered huge demand for rechargeable batteries, but many of these batteries are now in bursting into flames in places you would least expect. vinita nair is looking into this. >> reporter: when the fire first ignited, employees at this kentucky gas station thought it was a bomb.uc it turned out to be an e- cigarette that exploded in josh hamilton's pants.in he suffered third degree burns. it's just the latest incident involving defective lithium ion batteries that power e-er cigarettes. 21-year-old evan spahlinger had to be placed in a medically induced coma for three days after one of them blew up in his mouth. >> it's an alternative to smoking cigarettes. it it's supposed to be a safer andy a healthier way of doing it.er >> reporter: the same battery

also power hoverboards. since december there have been 52 reported incidents involving hoverboards catching on fire. jay whitacre is a professor at carnegie mellon university. he said the demand to make these products cheaper and more powerful has led some companies to cut corners. >> what we're seeing right now is a situation where maybe some of these batteries are simplyt not made to the same standard as the battery that are made say, at sony or panasonic, which haveor much more stringent quality control. >> reporter: whitacre says that lithium-ion-powered items likeit e-cigarettes and hoverboards are considered high-power applications. if their batteries are badly designed when they are charged they can overheat. is it something that the user is doing incorrectly? >> no. in general, with this kind of t technology, it's very difficult for the user to be at fault.en there is a well-controlledt charging circuit, and there should be a good package that the cell lives in.th both of those things should be

>> reporter: industry advocates say these incidents are still rare and that users shouldsh always use compatible batteries and chargers. they say to avoid batterytt contact with metal objects, scott, such as coins, keys, or jewelry. >> pelley: vinita nair, thank you very much. there's a plan to give wider air passengers wider seats. we'll get to the bottom of it. and a young fan bags quite a gift from a legend when the cbs even news continues. go, go, go, go, go, go... touchdown! choir and harp music. this place, it's the best-kept secret in football since... hey, how did he get in here?! and with toe nail fungus! fight it! with jublia. jublia is a prescription medicine used to treat toenail fungus. use jublia as instructed by your doctor.

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and better nutrition in so many varieties. classic. cage free. and organic. only eggland's best. better taste. better nutrition. better eggs. what backache? what sore wrist? what headache? advil makes pain a distant memory. nothing works faster stronger or longer what pain? advil. >> pelley: airbus has an idea a that could revolutionize the in- flight experience. think flying station wagon. here's kris van cleave.ve >> reporter: jet maker airbus wants to patent a seating concept taking a row of three airline seats and turning it into a rapidly and easily reconfigurable bench.ra it could seat the traditionalif three passengers, shift to two people who need additional space, including overweight

person, like two parents and two small children.>> >> the airlines will consider anything that allows them to make a buck. >> reporter: ben mutzabaugh is the editor of "usa today's" "today in the sky" blog. >> if we've seen nothing else in the airline industry, they're very clever about coming up withge ways to sell seats to passengers, especially when they can charge more for either seats that are better or for seats that are less awful. >> reporter: airbus previously sought patents for a design stacking passengers and this semi-standing concept. seat maker zodiac created a hexagon pattern where the middle seat faces the passengers in the aisle and window while adding up to 30 more passengers per plane. tennessee congressman stephen cohen worries extra seats could jeopardize safety making it hard to evacuate within the required 90 seconds as seen in this video. he's authored a bill requiring a the f.a.a. to set minimum seat- size standards. >> if people can't get out of an airplane in emergency conditions

it shouldn't be after an accident.ft after there's an accident, it's too late and people are dead. >> reporter: the big question now, scott, will an airline say they want these seats and will safety regulators ever allow them to be installed in a plane? >> pelley: kris van cleave, thank you, kris. what's killing players in the n.b.a.? wh stock prices, earnings, and dividends... an equity summary score that consolidates the stock ratings of top analysts into a single score... and $7.95 online u.s. equity trades, lower than td ameritrade, schwab, and e-trade, you realize the smartest investing idea isn't just what you invest in,

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i'm jerry bell the second. and i'm jerry bell the third. i'm like a big bear and he's my little cub. this little guy is non-stop. he's always hanging out with his friends. you've got to be prepared to sit at the edge of your seat and be ready to get up. there's no "deep couch sitting." definitely not good for my back. this is the part i really don't like right here. (doorbell) what's that? a package! it's a swiffer wetjet. it almost feels like it's moving itself. this is kind of fun. that comes from my floor? eww! this is deep couch sitting. [jerry bell iii] deep couch sitting! >> pelley: heart problems account for three-quarters of sports-related deaths in young athletes. now, a new study may help saveay lives, and here's dr. jon lapook. >> reporter: two years ago, isaiah austin was one of the nation's top college basketball players. then, a physical before the n.b.a. draft revealed a heart problem, ending his career. >> i just didn't know what to do

know, just accepting it, accepting that life and health is more important than a game. >> reporter: in the u.s., sports-related sudden cardiacn death is highest among basketball players.ig one big question is what's a normal heart size for these athletes? to find out, dr. david engel and colleagues reviewed the heart ultrasounds of more than 500 n.b.a. players. when you first saw them, you thought these are big hearts. these are abnormal? >> the first instinct is to say these hearts are enlarged. we're not used to seeing hearts for people that are this big. the average n.b.a. player is 6'7" and the average weight is 222 pounds. >> reporter: it turns out, like any other muscle, the heart gets t bigger with exercise, although the hearts of the n.b.a. players were about 10% thicker than normal, that was not felt to be dangerous. the research establishes a baseline for doctors going forward. and how does this help us? >> this should help us distinguish those changes from dangerous heart conditions thatda

death. >> reporter: in addition, they found that the aorta, the major artery leaving the heart, is also bigger in these athletes and knowing that will help with future diagnosis. scott, dr. engel says this is now a model for evaluating athletes in other sports. >> pelley: jon lapook, thank you very much, jon. well, soccer's biggest star came through with heart today for his biggest fan. fan. a five-year-old was photographed wearing a lionel messi shirt made from a plastic bag. it went online and messi sent him an autographed shirt from argentina's national team. the bag has been retired. up next, a math teacher's formula for success against the odds.a for success against the odds. so let's start talking about your long term goals. knowing your future is about more than just you.

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>> pelley: we end tonight with aon solution to a math problem that has stumped the best minds for centuries. how do you get school kids to succeed at calculus? here's mireya villarreal. >> reporter: from the outside, lincoln high school does not look like a place that inspires greatness. old, with gates on the windows,at in a tough east l.a. neighborhood. >> today is all about making your life easier. >> reporter: but look beyond all of that, and you'll find thisou man, anthony yom. >> this is almost similar to this guy right here, right? >> reporter: the son of korean immigrants, yom teaches what isch considered the hardest class inid school, advanced placement calculus. >> one of my strategies, really to make sure to provide that environment where kids are not shamed of asking questions. do you get it? >> reporter: his approach to teaching goes beyond calculating the slope of a curve. yom makes his class meet after school, on weekends, and even sc holidays.

>> it's not always fun, but i do know for sure, once they get the score and if i ask them, "hey, was it worth it?" every single one of them say itt was so worth it. >> reporter: for three years in a row, every student that has walked into his class has passed the a.p. calculus test. and this year, one student, cedrick argueta, got every question right. >> his style of teaching commands respect and his personality is very likable. he gets to know his students on a personal level. >> reporter: what is the secret s here? >> they know that i sincerely care about them, and it's prep for them. >> reporter: with love? >> yeah, with love. >> reporter: cedrick argueta and yom were both ordered by the l.a. school board and president obama invited cedrick to the white house science fair. the 17-year-old wants to go to cal-tech and become a rocket scientist, while yom's focus is

students. eric:"i was wrong...donald trump is real...and the republican

going to have to deal with that in some way." even local pundits are surprised at donald trump's success so far. and nevada's non-partisan voters may have even more clout than either party in this election. campaign 2016 tops channel 2 news at 6:30 the number of nonpartisan voters in the silver state is growing faster than either main political party. good evening and thanks for joining us. i'm kristen remington. and i'm landon miller. those nonpartisan voters are becoming more and more powerful in terms of keeping nevada a swing state. erin breen joins us from the newsroom with the latest statistics on voter registration and on how some say nonpartisans are adding to trump's success. donald trump seems have struck a chord with voters tired of washington politics and focused on change. and some say that's why his unexpected success continues to snowball.

nonpartisan voters could have more power than either party. his statements have been outrageous...yet his popularity continues to grow? donald trump is a political anomoly...one that has stumped the pundits. eric:"four months ago i would have said trump will fade...implode...whateve r. but he's captured what i call the anger demographic. it's i'm mad at government..i'm mad at washington...i'm just mad." and it seems to be in all categories... trump :"we won with the young...we won withi the old....we won with the4 highly educated....we won with the porrly educated...i love the poorly educated!" and...he's pulling in the indepedent voters. new hampshire allows non partisans to vote in their caucuses...and herzik says ... they made quite eric:"they voted disproportionately in the republican party...and for donald trump...he won that demographic."