After 2 years and $2 billion, it's time to choose (CBS News) Two years. $2 billion. Now it's your turn. The long and expensive presidential campaign is down to its last hours. National polls show the race dead even, but in the few swing states that will tip the balance, the president has a slight advantage over Mitt Romney. In Ohio, the University of Cincinnati shows the president ahead 50 percent to 49 percent. In Florida, a recent poll has Mr. Obama ahead by just two points. In Wisconsin, the president leads by three points. In Iowa, the Des Moines Register shows Mr. Obama ahead 47 percent to 42 percent. A Colorado poll puts the president up two points. Complete coverage: Election 2012 Polls: on election eve, presidential race a toss-up When will we know a winner on election night? CBS News correspondent Nancy Cordes reports the president holds his 101st and final campaign rally in Des Moines Monday night for two reasons: First, Iowa is one of the battleground states the campaign feels most confident it can win; and second, it is the state that catapulted him toward the presidency five years ago with that upset victory in the Iowa caucuses. President Obama has spent the past 48 hours in seven states -- three time zones -- surrendering sleep and his voice in pursuit of a second term. This is not just a choice between two candidates or two parties. It is a choice between two visions for America. A choice between returning to the top down policies that crashed our economy, or a vision that says we've got to build a strong foundation, based on a strong and growing middle class, an opportunity for everybody, not just some," Obama told a crowd in Columbus, Oh. In these final frantic days he's been embraced by Bill Clinton in New Hampshire, serenaded by Bruce Springsteen in Madison and Stevie Wonder in Cincinnati. On Monday, Mr. Obama had this message for supporters who may have lost some faith over the last four years: "You know where I stand. You know I tell the truth. And you know I'll fight for you and your families every single day as hard as I know how! You know that about me! A top aide tells CBS News that over the past few days the president has grown visibly more relaxed as he slides from rally to rally on Air Force One, first because he's very confident in the outcome but also because he knows that no matter what happens Tuesday, this is the last race he'll ever run. The Obama campaign may have confidence, but they can read the polls, too: Just have a look at the president's travel schedule Monday alone -- barnstorming three swing states, plus his home state of Illinois. CBS News correspondent Jan Crawford reports Mitt Romney is on a similar tour, working four swing states Monday to make up those paper-thin deficits. Over the weekend, one of Romney's senior advisers spoke to CBS News and after being asked what he had planned for the final days, he had a one-word answer and he said: "praying." He laughed and said it with a smile, but it reflected the underlying tension and uncertainty in a race that could not be any closer. At a recent campaign stop, Romney said: "If you believe we can do better and if you believe America should be on a better course, and if you're tired of being tired, then I ask you to vote and work for real change." With the campaign in its final hours, Romney's hitting four toss up states Monday after a weekend of crisscrossing the country, as he tries to close out the race with the win. This is much more than our moment. It's America's moment of renewal and purpose and optimism. And we've journeyed far and wide in this great campaign for America's future. And now we're almost home. One final push is going to get us there," Romney said. Romney is still expressing confidence. But in Ohio, Sunday, he acknowledged with a touch of humor the chance the President could win. "If the president were to be reelected he would," Romney said before being interrupted by boos from the crowd. It's possible, but not likely. The strain of the campaign is showing, especially on Ann Romney, who said she was emotional as she looked back: "It's really humbling. It's very touching. And as they took in a large crowd at a Colorado rally this weekend, both Romneys seemed to recognize the hard fought race was nearing an end, though it's not over yet. From Ohio, Romney flies Monday night to New Hampshire for a final rally. That, of course, is the state where he kicked off his campaign. On Election Day, he is right back in Ohio and then off to Pennsylvania. That's the state once considered safe for the president, but in this tight race anything could happen, and that, too, could be up for grabs.