I've been following John Edwards for an upcoming web piece, but tonight I'm at the hottest show in Des Moines, Barack Obama's rally at a South Side middle school. Compared to an Edwards crowd, the folks here are much younger, including high school and college students and plenty of young families. There's no visible union presence. Many of these Iowans will be first-time caucus-goers, and the campaign warms up the crowd with a question and answer session about how the process works. Like all the candidates, Obama runs late. While Edwards' holding soundtrack is 100 percent John Mellencamp (with whom he'll be appearing at a concert/rally here on Jan. 2), Obama's is, um, more colorful, and includes india.arie and soul classics. He takes the stage to the sounds of U2. Obama begins by speaking about his post-college job as a community organizer in a very different South Side, in Chicago. He introduces his young field organizers here in Cook County, and then asks the crowd how many are first-timer caucus-goers and how many are undecided -- about a third of the audience raises their hands in response to each question. "We are coming after you tonight! If we get you at the end of the night, please, fill out one of these supporter cards!" the candidate pleads. It's a more naked appeal than the one Edwards makes. Obama is funny and excited and riveting tonight. He hits many of the same anti-corporate themes as Edwards -- the gap between CEO and worker pay, the nefarious influence of drug and oil companies on policy making -- but his tone couldn't be more different. He talks not about "fight," but about unity. "The size of our problems are too big for a broken and divided politics to solve," he intones. "I ran because every American of every political stripe wanted a new kind of politics...that was focused less on ideology and more on practicality, that was focused less on spin and more on straight talk and common sense." That last bit sounds an awful lot like John McCain, of course, who Obama is currently battling for independent votes in New Hampshire. Obama devotes a minute toward the end of his speech to answering Edwards' accusation that he's "too nice" to bring change. "I "turned down the trial lawyer work to work as a civil rights attorney!" he shouts. Dig, dig. "Change is not going to happen because we don't listen to people...or because we holler at Republicans." He wraps up on the defense, assuring the crowd that he understands institutions like failing schools are resistant to reform, but that his life and American history have taught him to be hopeful about the possibility of change. And if you're a black man named Barack Obama running for president, he says, "You better be hopeful!" --Dana Goldstein