silent smile crashing all around me while i scream it out loud this is "nightline." >> tonight, ben carson under scrutiny and under attack. once mild mannered, he's now fighting back against those challenging his personal history. meanwhile, his fellow candidates were taking hitit their own in e gop debate tonight. but the question now is can carson get his momentum back? plus, he was one of the star witnesses at the o.j. simpson double murder trial. now the world's most infamous house guest is telling our barber walters, quote, they made a mistake. what he did with his former friend that night now taking on new significance. and why the world is standing up for heroes tonight. this veteran nearly lost her life over in afghanistan. now he's preparing for the

her incredible journey and what prprcearry has to do with it. but first, the "nightline 5." >> do you think your heartburn pill works fast? zantac works in as little as 30 minutes. when heartburn strikes, take zantac for faster relief as nexium or your money back. how much protein does your dog food have? 8%, 20%? real salmon and tuna has 30% protein. support your active dog's whole body health with purina one.

seconds. good evening on a high stakes night for the republican president 14u8 candidateses headadg into tonight's big

trump needed to prove he's a substantive candidate and jeb bush needed to demonstrate he's still a viable one. but perhaps most importantly dr. ben carson who has been surging in the polls neeeed to deal with the mounting questions about whether he's been honest about his own past. here's abc's david wright. >> reporter: it's a reality show higher. >> it sounds like a g ge show but it's not. >> reporter: this time next year right about now, in fact, one of the apprentice on that stage will either win 270 electoral you're fired.d. >> you're fired. you're fired. >> reporter: -- or not, one year from this week it's all over. >> so we begin. >> reporter: so the presidential reality show is getting realer by the day. tonight new jersey governor ris christie was voted off the island because of his poor poll numbers. >> the tribe has spoken. >> reporter: surviving to debate at the so-called kiddie t tle

like contestants on "the bachelor" or in her case, "the bachelorette" hoping to win that rose. two of the c cdidates are doing well enough to get secret service protection starting tomorrow. dr. ben carson, code named eli, now the front-runner. >> and people who know me know that i'm an honest person. >> reporter: and donald trump, code name mogul, running a strong second. >> we cannot let hillary clinton, who is the worst secretary of s ste in the history o o our untry, win this election. >> reporter: both of them pulling twice as much support as their next nearest competitor, according to the polls. between them, nearly 50% more than all the other gop candidates combined. one big question, will carson still be the front-runner after tonight? >> well, first of all, thank you for not asking me what i said in the tenth grade. i appreciate that. >> reporter: carson has been

>> i do not remember this level of scrutiny for one president barack obamamahen he was running. in fact, i remember just the opposite. >> he seems to feel like people have it in for him. >> the interesting thing is he thinks this is a tough week when really if you really look at where the stories are coming from, they're all deriving from one single source, his own words. this is just reporters asking questions about things he's said. >> reporter:r:eporters have been pouring over cacaon's unusual theory about the pyramids as outlined in a 1998 commencement speech. >> now, my own personal theory is that joseph built the pyramids in order to store grain. >> reporter: they've questioned specific details about his inspiring life story. and everyone has been scratching their heads over a story he's told many times about nearly stabbing someone to death years ago. >> i tried to stab him in the abdomen. and fortunately under his

clothing he had on a large metal belt buckle. >> reporter: so far reporters have beennnable to confirm the details of that incident, leaving a strange situation. a candidate insisting he almost murdered somebody and the skeptics doubting it. the irony is not lost on donald trump. >> this is the only election in history where you are better off if you stab somebody. a lot of weird things are happening. this is a strange election, isn't it? >> reporter:r:onight this from carson on the vetting issue. >> i have no problem with being vetted. what i do have a problem with is being lied about. and then putting that out there as truth. >> reporter: but for the most part tonight's debate was distinguished by the absence of sharp attacks. tonight the moderateors steered clear of any inkling they were going for a gotcha. their question -- >> what specific steps would you take to balance the budget. >> reporter: substantive.

>> how do you reassure americans their jobs -- >> excellent questionon >> reporter: pointedly unpointed. >> what specific regulations would you change and how will that lead to jobs and growth? >> reporter: fox business clearly sought to avoid any suggestion they were trying to provoke a food fight. >> business issues can be riveting. >> reporter: the other candidates, that made it all the more difficult to force a make or break moment. so did anybody succeed? >> i think this debate now is show that basically we're probably down to four candidates this race is, which is ben carson, donald trump, ted cruz, and marco rubio. >> reporter: well, on trump's biggdea to build a wall to keep illegal immigrants out, which he himself parodied on snl -- >> the president of mexico is here to see you. >> donald. >> enrique. >> i brought you the check for the wall. . >> oh, that's s s wonderful. >> we will have a wall. the wall will be built. the wall will be successful. and if you think walls don't

work, all you have to do is ask israel. >> reporter: kasich tried to top the wall. >> silly argument. it's not -- you should let jeb speak. it's unfair. >> reporter: bush tried to climb over the wall. >> thank you, donald, for allowing me to speak at the debate. that's really nice of you. really appreciate that. >> reporter: the candidates providing the fireworks while the panel pretty much ducked. >> they're doing high fives in the clinton campaign right now when they hear this. that's the problem with this. we have to win the presidency. >> reporter: carly fiorina scored points off trump and his boast that he's on great terms with vladimir putin. >> i got to know him very well because we were both on "60 minutes." >> i have met him as well, not in a green room for a show but in a private meeting. >> reporter: trump clearly growowg annoyed with her. >> why does she keep interrupting everybody? >> yeah. boy. >> terrible. >> reporter: a strong performance from many of them.

we will be the party of the 21st century. >> i believe in america. if we get back to the free market principles and constitutional liberties that built this country, we can turn this country around. >> i think the winners tonight were probably marco rubio and ted cruz. if i was putting on a bet on a stock i would put them as buy. i would put jeb as a sell. >> reporter: immediately after the debate signed off, hillary clinton's campaign tweeted out this image of her looking bored. #gopdebate. i'm david wright for "nightline" in new york. > up next here on "nightline," barbara walters with a fascinating "where are they now" story. kate oh kaelin, the house guest

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kato kaelin shot to fame 20 years ago in the o.j. simp sompn trial. he was the star witness. and where is he now and which does he think about his former

here's abc's barbara kato, in your opinion, do you think he murdered nicole and ron? >> yes. >> reporter: you may remember kato as a witness in the trial. a tenant in jimp son's guest house. a struggling actor who is both a friend to o.j. and nicole. he became an overnightelebrity after his trial testimony. kato helped establish a timeline for investigators me sat down with me recently to share his recollections. >> o.j. simpson, he's very much a character out of shakespeare play. here's a man who had everything and lost everything and became, from a adored athlete to a pariah. >> we will bring you up to the minute news on o.j. simpson. >> reporter: my introduction on the simpson case began on liv

television as hugh downs and i went on air on "20/20." their bodies had been discovered outside nicole's'some i i brentwood. it was a grisly crime scene. >> if i saw o.j. today i would say, o.j., did you do it? >> and what do you think the answer is?? >> what would i think he would say? i think he would say absolutely not. >> approximately what time was it when you got your food? >> 9:25. 9:26. >eporter: his testimony would bookmark both ends of what the prosecution argued was the time period period in which simpson could commit the crime. >> o.j. simpson came by my guest house and he knocked on my door d said he was going to go out to eat. went to mcdonald's. >> reporter: the prosecution's opportunity clock began at 9:36 p.m. when o.j. and kato returned to rockingham. kato went to his bungalow, o.j. to his house.

an hour and ten minutes later a limousine arrived to take simpson to the airport. >> he killed her out of jealousy. >> reporter: the means of the crime according to the prosecution was a knife that was never found. >> you saw o.j. get into the limo. tell us about that. >> i waselping pack stuff into the limo because he was going to chicago and there was a bag that was ready to be packed. he said, don't touch this bag and that bag was never found. >> a suitcase type bag? >> looked like a backpack. >> now do you think it may have been the murder weapon? >> i don't know what was in there but something in tre enough for o.j. simpson to say don't touch. >> never was found? >> never was found. >> y y are reminded that you must not be influenced by mere sentiment, conjecture, or public feeling. >> reporter: the jurors found out and then reached a verdict in less than four hours of deliberation.

defendant orenthal jay switch son not guilty of the crime of murder pony coal brown simpson. a nell nippon nicole brown simpson, a human being. >> count one of the information. >> we were togetherer you and i, in los angeles when the verdict of not guilty came out. you were shocked. i remember your face. >> i remember that because you asked me, i think off camera, you said, what do you think? i whispered in your ear, i said, i think they made a mistake. >> you still feel that way? >> yeah. >> reporter: kato kaelin still has some of his boyish looks 20 years later but his life is very different. >> i used to call you america's favorite house guest because you lived in the guest house of o.j. now you own your own home, you have your own business. tell us about your life. >> yeah,,t's good. my goal actually one day in life is to have someone live behind me. but, yeah, what i'm doing now is

clothing line, barbara, it's calledslacker. >> wait a minute. is that auto biographical? >> no, but people would call me, he's the biggest slacker. i said, take that and i came up with this product line called slacker. >eporter: ron goldman's family spearheaded by his father and sister kim went after simpson in a civil suit, charging him with responsibility for ron's murder. they won big time. the jury found simpson culpable and awarded a judgment of $33 mimiion. >> mr. goldman, what's your reaction? your reaction? >> wonderful! >> reporter: o.j. simpson suffered severe financial consequences me didn't have the $33 million the jury awarded them. and goldmans have had trouble collecting. so far they have received only a

but he would soon faceet another jury. simpson was convicted of robbing a dealer of football memorabilia at gun point and stealing back mementos and souvenirs that used to belong to him. a hotel camera caught him on tape. >> we were just robbed at gun point by o.j. simpson. can you send pleasehere, please. >> my lawyer told me you can't break in hisis room. >> reporter: the sentence was serious jail time, 9 to 33 years. he is in prison now, but not for murder, not for killing nicole. >> right. and i think him being in prison, i'm not such a believer in karma but i switch my mind mind to that because i think karma came back to him. >> orenthal. >> when nevada convicted him it almost felt like, hey, l.a., this is how you do a trial. >> we should say that barbara

scandals" monony nights at 10:00 eastern on investigation discovery. coming up next on "nightline," she went from near death of a battlefield calamity to hitting the slopes. how did she do it and what is her mission now? abc news "nightline" brought to you by e trade. good. very good. you see something moving off the shelves and your first thought is to investigate the company. you are type e . yes, investment opportunities can be anywhere... or not. but you know the difference. e trade's bar code scanner. shorten the distance between intuition and action. e trade opportunity is everywhere. yeah. that's the one right? we forgot dave! thank you.

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