As we come on the air, president obama and governor romney are preparing for the super bowl of politics. 60 million americans expected to watch the first debate tonight. And it is one of those nights... See More
As we come on the air, president obama and governor romney are preparing for the super bowl of politics. 60 million americans expected to watch the first debate tonight. And it is one of those nights that can change history. We want to show you the stage, right now, at the university of denver in colorado. It is standing by, awaiting the candidates. 34 days until your voice, your vote. And the abc news political team is right there in that room. David muir and jake tapper, ready for the opening round to begin. So, david, start us off. Reporter: Diane, good evening from the debate hall here at the university of denver. You can see the stage behind me. Everything planned right down to the minute tonight. President obama will enter from the right. The governor from massachusetts, governor romney entering from the left. To give you an idea of the setting here, about 1,000 people inside this debate hall, when it starts. Look behind the cameras tonight. We're inside a hockey arena that normally seats 8,000 but they've created this intimate setting as tens of millions watch from their living rooms tonight. When president obama and mitt romney walk onto that stage tonight, it will be the first time they've met face to face in four years. Last time, during the presidential race in 2008, during those back-to-back democratic and republican presidential debates during the primaries when candidates from both sides were called on the stage, it was senator obama and governor romney talking. The president congratulated romney when he clinched the republican nomination and this moment in 2007, a labor day parade in 2007. Good luck to you today. Reporter: But tonight, they will shake hands in front of millions watching, before debating each other for the first time. In a format that is more free wheeling, no strict time limits for answers. Creating an environment in which the two will be able to challenge one another. Every detail here set for tonight, both campaigns flipping a coin. The president will be introduced first, he'll get the first question. The romney campaign winning the toss on closing arguments. Governor romney will get the final word tonight. Even a coin toss over the wives. Mrs. Romney will be introduced first. Both wives playing the role of debate partner. Mrs. Romney telling cnn it's been her most important role during the campaign. It's a cute thing that he does, almost after every answer. He finds me in the audience. The first thing he does on stage, he takes off his watch, he puts it on the podium. But then he writes "dad." Reporter: Romney's father, who also ran for president. And the first lady acknowledging her own nerves. I get so nervous at these debates, and, I'm like one of those parents watching their kid on the balance beam. You just are standing there, trying not to, you know, have any expression at all. Reporter: Advice that comes on the same day they mark something else. This is from me to you, honey, happy 20th anniversary. Reporter: They will likely mark their anniversary with a private dinner after the e the bait tonight. Sasha and malia back in washington, they have school tomorrow. Several of the romney boys will be here. And we took this image today, tweeted it out. Look at this. The debate prep you don't see. "Wet paint" the sign up on the stage in the last 24 hours. We checked it out for you before we came on tonight. The sign is down, everything is ready to go.
This transcript has been automatically generated and may not be 100% accurate.