ask tonight on "nightline," four more years. it was president obama's big night at the highly anticipated finale of the democratic national convention, but did he convince voters that the best is yet to come? his secret weapon, she introduced the president tonight and two nights ago, she brought down the house here. michele obama looks back and forward with diane sawyer and talked about how her kids reacted to her big speech. and the spin doctor. he works with jay-z and oprah, now he's spinning tunes at this convention, like "signed sealed delivered." we hang with him to find out how the democrats get down.

this is a special edition of "nightline." your voice, your vote, the democratic national convention. >> good evening, i'm terry moran here in charlotte, north carolina, where the 2012 democratic convention has entered the history books with a speech by president barack obama. a stirring speech for the people here in the hall. he launched a vigorous defense of his record, several negative attacks against mitt romney and he offered the delegates a and democrats a little bit of that old-time obama religion of hope. all in all, the people who were in this hall, received this speech. they were electrified by it. they were explosive at times. you could hear them yearning for his success. the real question is, how does

this play outside the hall, in the country with you? because the president has significant challenges ahead of him. ♪ they still love him. barack obama may be struggling in the polls and fighting for his political life, but tonight among the democrats gathered here, any doubts or disappointment seemed to disappear. >> madam chairwoman, delegates, i accept your nomination for president of the united states. [ cheers and applause ] >> reporter: still, you couldn't help but think what a difference four years have made. he's so much grayer now, the toll the presidency takes, that youthful aura that still clung to barack obama in 2008, has been burned away by the searing pressures of power. so he spoke tonight as a man of hard and sometimes bitter experience, of survival. >> i recognize that times have

changed since i first spoke to this convention. times have changed and so have i. i'm no longer just a candidate. i'm the president. [ cheers and applause ] >> reporter: this was a political party that will need every once of effort to re-elect president obama. that's why you saw former congresswoman gabby giffords unite this hall in tears and cheers as she recited the pledge of allegiance. >> reporter: and that's why vice president joe biden went all out too. >> we can now proudly say what you've heard me say the last six months. osama bin laden is dead and general motors is alive. [ cheers and applause ] >> reporter: the president did something else. he addressed directly the frustrated hopes and mixed feelings about his leadership out across the country.

>> now, i won't pretend the path i'm offering is quick or easy. i never have. you didn't elect me to tell you what you wanted to hear. you elected me to tell you the truth. [ applause ] and the truth is, it will take more than a few years for us to solve challenges that have built up over decades. >> reporter: truth and struggle. ♪ >> reporter: a long way, perhaps, from the euphoria of hope and change. this was really the president's biggest challenge tonight, the biggest challenge in his campaign, to overcome the disappointments and the doubts among so many americans who voted for him in 2008. and give them hope again. >> i think they're looking for the combination of that vision, the hope that he offered in '08, plus, the reality of, this is how we're going to do it.

>> reporter: we chatted with the author of the definitive biography of obama so far. >> what happened with the 2008 voters who were so full of hope? they were so ecstatic! what happened to the hope? >> i think in one sense, obama went into office thinking that he could somehow transform this place. but he didn't really have the experience in washington to understand what it would take to try to bring things together. >> reporter: somewhere it seemed obama stopped driving events and seemed more driven bipartisan cyclones and fierce economic head winds. but that's not supposed to happen to strong presidents. a republican ad mocked his efforts to explain. >> barack obama's got lots of excuses for the bad economy. >> headwinds coming from europe. >> we've had a string of bad luck.

>> an earthquake in japan. >> reporter: and in 2008, he promised so much more. >> this was the moment when the rise of the oceans began to slow and our planet began to heal. >> rolling back the bush tax cuts on the top 1%. >> as we took a stroll through the delegations today, we heard democrats fire back in the president's defense. >> everyone did expect hope and change and they expected it instantaneously. however, the mess was created over a lengthy period of time. >> it's a partisan fight to the death, this campaign. so obama went negative, early and often, unusually for an incumbent president. >> when governor romney and his friends in congress tell us we can lower our deficits by spending trillions more on new tax breaks for the wealthy, what did bill clinton call it? you do the arithmetic. i refuse to ask middle-class families to give up their deductions for owning a home or raising their kids just to pay for another millionaire's tax cuts. >> reporter: in the end, it was,

once again, that barack obama spoke of hope in tough times. >> america, i never said this journey would be easy, and i won't promise that now. yes, our path is harder, but it leads to a better place. yes, our road is longer, but we travel it together. we don't turn back. we leave no one behind. we pull each other up. we draw strength from our victories, and we learn from our mistakes. but we keep our eye fixed on the distant horizon, knowing that providence is with us, and that we are surely blessed to be citizens of the greatest nation on earth. >> reporter: president obama leading the democratic party into the battle into the fall. next up, she brought down the house here a couple nights ago. first lady michele obama back on stage tonight. she sat down with diane sawyer

to talk about how their daughters thought of her big speech the other night. up next. abc news "nightline" brought to you by -- [ diana ] power was very important to me. we test-drove the camry, took it on the freeway,

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tonight first lady michele obama had her second big moment up on that stage there as she introduced her husband for his big convention speech. couple of nights after she brought the house down with her own passionate defense of barack obama. but the stamp of approval that meant the most to her is what her two daughters -- their two daughters thought of her speech as she told abc's dianne sawyer. >> and the president of the united states of america, barack

obama! >> she was there with her husband for his big moment tonight. ♪ >> michele, i love you so much. a few nights ago, everybody was reminded just what a lucky man i am. [ applause ] >> reporter: her own speech had launched this convention on tuesday and enthralled the convention floor. >> i see the concern in his eyes, and i hear the determination in his voice as he tells me, you won't believe what these folks are going through, michele. it's not right. we've got to keep working to fix this. we've got so much more to do. >> reporter: it was a personal story with a deeply political sub text. afterwards, a phone call from the white house. >> what did the president and your daughter say to you? >> they called me in the car, and the girls had already gone to bed because he said they were exhausted. it was a late speech, but he said he was so proud. >> and then the fan with the

fewest words. 11-year-old sasha. >> the next day i called home, talked to sasha, the youngest, who never compliments me on anything. she said, you know, mom, you gave a really good speech last night. she said, all my friends told me to tell you what a good job you did. >> i was like that's so sweet, honey. >> wow. >> my 11-year-old, i'll take it and run. >> so much of the speech reflecting on the essential focus of her life, family. ta. >> the kids have gotten so big, i think that's what barack and i look at. we really measure things by how much the girls have grown. >> we can see the physical difference. we can see the height. what's the other most surprising change in them? >> i am pleasantly surprised at how normal they are. they are level-headed. they work hard. they care about people. and they don't take their position for granted.

but they definitely don't, in any way exploit it or show any signs of entitlement. they're just good, solid kids. >> we showed her photos of her daughters in 2004. >> oh, my goodness, this was barack becoming a u.s. senator. i remember this so clearly. so how little sasha is. she walked up to vice president cheney, he reached out his hand to shake her hand. she slapped him a high-five and then she turned around and waved at the cameras and i thought, oh, my god, here we go. >> and here they go, again. this marathon run for a second term. by the way, she never mentioned the republican nominee in her speech by name. >> because for barack, success isn't about how much money you make. it's about the difference you make in people's lives. >> and her message seemed unmistakable. >> so in the end, for barack, these issues aren't political.

they're personal. >> and her impact, not lost on the last democrat to be elected to a second term. >> i want a man who had the good sense to marry michele obama. >> by the way, in political terms, a kind of volcano, social media, tweeting 28,000 tweets a minute during her speech. >> do you know that you had 28,000 tweets? >> is that good? i don't know what is that? is that good? >> i would say that's good. >> i don't know how to measure it. justin bieber gets more tweets than that. that's probably nothing. my kids might laugh at that, 28,000 tweets. >> you're setting a high standard for yourself. >> i just don't know. >> first lady michele obama, no question about it, a major asset to her husband's campaign. next up, what do beyonce, diddy, and barack obama have in common?and barack obama have in >> well, this famous dejay.

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for people inside the hall, music is absolutely critical. it sets the mood, gets people going. at this convention, they used a deejay, whose client list includes people like jennifer

lopez and kanye west. se celia vega triangled along with the man who drops the beats for the democrats. ♪ >> reporter: tonight in charlotte, a handful of a-list stars were center stage. mary j. blige brought down the house. ♪ >> reporter: marc anthony belted out the national anthem. ♪ >> reporter: even scarlet johansen made the pitch. re-elect president barack obama. >> reporter: but there is one secret weapon of hipness, this campaign has in its back pocket. a celebrity deejay. beyonce and kim kardashian hired him to play at their weddings. he can rake in up to $100,000 for a single gig. deejay cassidy is jamming his way through this campaign.

hoping a little madonna might bring some cool into this cold convention hall. >> we got journey, teddy pendergrass, marvin gaye, stevie wonder. >> barry white would go a long way with equal opportunity. >> but you know, it all works. we're here, like i said, to learn and to celebrate and decide the future. >> his real name is cassidy. >> by 18 he was partying with models is spinning-for-p diddy, even jammed at the president's birthday. >> it's a big ticket item? it's your top secret file. >> i guess so, sign, sealed and delivered. ♪ oh, baby here i am, signed, sealed, delivered i'm yours ♪ >> reporter: that was his too. he works with the campaign to choose the perfect song.

with his trademark top hat and gold microphone, sitting always in the best seat in the house. >> this is like watching c-span, you must be the most well informed citizen. i wish every young person my age would actually be home and have this on tv. >> hold on a second. ♪ >> reporter: did you watch much of the republican convention? >> i watched some. >> what did you think of the music selection? >> i didn't think much. >> ouch. >> i'm just being polite. >> if there are doubts about whether the hope has faded, the buzz has died, the cool has gone, the faithful celebrities aren't buying it. they're in the convention like will a -- will im and ashley judd, all hosting the

after parties like eva longoria and slow ridea at a local charlotte dive. >> you feel like it's the same as it was four years ago? >> absolutely. >> as the clock strikes 1:00 a.m., it looks like animal house took over capitol hill, thanks to a little jackson five. ♪ >> at the after party, the energy doubles. >> how long does this party go? >> until they leave. >> reporter: for the dejay cassidy, the goal is to keep the party going all the way to november 6. >> who's ready for four more years of president obama? >> the deejay here at the convention. thanks to cecilia for that. >> but the real music are the oratory and the speeches in the hall. does it stir up the voters and stir up the base? to care riff barack obama or mitt romney to victory? thanks for watching abc news. stay tuned. in the morning, good morning america is working while you're