CHARITON, Iowa, Nov. 8 -- Sen. Barack Obama (Ill.) took on his two principal rivals for the Democratic presidential nomination Thursday, arguing that Sen. Hillary Rodham Clinton (N.Y.) cannot appeal to independents and Republicans as effectively as he can and asserting that former senator John Edwards's populist message does not square with his record.
But even as he was challenging Clinton and Edwards (N.C.), Obama said he would resist pressure from supporters and others to go sharply negative in his bid for the nomination, saying that would undermine his effort to bring a close to an era of polarizing politics.
Aboard his campaign bus as he rolled through southeast Iowa on Thursday afternoon, Obama spoke frankly about the difficult balancing act of drawing ever sharper distinctions with his opponents, particularly Clinton, without succumbing to going negative to overtake a front-runner.
"I want to campaign the same way I govern, which is to respond directly and forcefully with the truth," Obama said. "That means I'm not going to paint a caricature of Senator Clinton. I think she's a smart, able person. I think anybody who tries to paint her as all negative is engaging in caricature, and when you start slipping into that mode, it's hard to come back."
He acknowledged that some might interpret that as a sign of timidity but said that he is convinced there is no other way for him to try to win the nomination. "First of all, you start losing credibility," he said. "Secondly, I'm not that good at saying things I don't really believe. Maybe this is considered a weakness in my political style. I try to stick to what I think."
Obama also defended his support for giving driver's licenses to illegal immigrants, a flash point in the Democratic race the past two weeks, and acknowledged that the eventual nominee will face a barrage of criticism from Republicans on the issue of immigration.
He also sought to explain a recent shift in his message on Social Security, an issue on which he has accused Clinton of not being forthcoming.
The interview came midway through a five-day stint in Iowa and at a time when he has been far more pointed in talking about his rivals. With less than 60 days until the Iowa caucuses, Obama has been trying to make a forceful case that he can do what no other Democrat in the race can: bring independents and Republicans to support his candidacy in a general election.
Democrats, he said, have an opportunity to rebuild their party, but only if they seize what he calls a unique opportunity, and he argues that he can redraw the political map in a way Clinton cannot.
"Whatever arguments you want to make for Hillary Clinton, I don't think anybody believes that somehow the election is going to be significantly different than 2000 or 2004, that different states or different congressional districts suddenly come into play, that she brings in a whole new group of voters that might not have voted before."
Edwards, who has staked his candidacy on winning the Iowa caucuses, has turned his attention to Obama recently, arguing that the Illinois senator would be too willing to compromise with special interests as president. The former North Carolina senator has said the next president must be willing to fight those interests.
Obama suggested Edwards had reconstituted himself since his last campaign. "John wasn't this raging populist four years ago when he ran" for the previous Democratic nomination, he said. "He certainly wasn't when he ran for the U.S. Senate. He was in the U.S. Senate for six years, and as far as I can tell wasn't taking on the lobbyists and special interests. It's a matter of, do you walk the walk that you talk?"
Obama also said he stacks up favorably against Edwards when their earlier records are compared. "Let me put it this way," he said. "If John wants to make the comparison between the work I did as a community organizer -- or as a civil rights attorney or as a state senator taking on special interests -- to him working as a trial lawyer making millions of dollars, I'm happy to have that discussion."
Obama reiterated support for the controversial idea of allowing illegal immigrants to apply for driver's licenses, the issue that created an uproar in the Democratic debate in Philadelphia a week ago. Clinton's halting answer to a related question provided her opponents an opportunity to attack her for refusing to state clearly where she stands on volatile issues.
Obama backed a similar measure as an Illinois state senator and said Thursday, "I would not overrule a state that has decided for public safety purposes that this is the best way to do it."
Obama faced repeated questions about illegal immigration from his Democratic audiences this week and acknowledged that Republicans will make the issue a central part of their campaign.
"My estimation is the Republicans will run on two issues, and two issues only: terrorism and immigration," he said, adding: "There's no doubt there will be attempts made to hit whoever the Democratic nominee is on this issue. And we have to stand our ground and not be defensive."
On Social Security, Obama had previously said that everything would be on the table for discussion as part of negotiations to secure the system's future solvency, including raising the retirement age and reducing benefits. Now he says he prefers raising the cap on the portion of a worker's wages subject to payroll taxes.
"When I said all things are on the table . . . that doesn't mean I don't have clear opinions about how I think we should best proceed," Obama said.
In contrast to Clinton, Obama said he would offer his own Social Security proposal as president and that he would hope to have gained a mandate for changing the system through the campaign.
As the interview drew to a close, Obama expressed great confidence in his ability to change the political environment -- and the political map in America. Asked what red states he could win, he named Virginia and added provocatively, "I think I can put Mississippi in play" because of the high percentage of African Americans in the state, despite the fact that it has been one of the most reliably Republican states in the nation."
in an interview that was also conducted on a bus.