BURLINGTON, Iowa — Barack Obama sealed the deal Saturday with Hal Geren.

Geren entered an Obama campaign event unsure of whom to support in next week's Iowa caucuses. He left as an Obama backer, convinced that the Illinois senator has what it takes to win the election and shake up Washington.

"I think he's a lot tougher than people think," said Geren, a 56-year-old postal service employee. "He's not afraid to stand up."

Obama spent much of Saturday courting undecided Iowa voters with an argument that he has the political skills to win the presidential election but none of the baggage carried by Democratic rivals John Edwards and Hillary Rodham Clinton. He boasted that a recent poll showed he could beat the five major Republican candidates, while Edwards or Clinton could not.

"Part of the problem John Edwards would have in a general election is that the issues he's taking out now are not the things he was saying four years ago, which always causes problems in the general election," Obama told about 400 people at a Keokuk high school. "And Sen. Clinton doesn't beat all five of them because you start out with half the country not wanting to vote for her."

Obama argued that his message of inclusion and consensus amounts to "a politics of addition" that will attract independents and even some Republicans in November.

That argument resonated with Brian Hagmeier, who attended an Obama speech wearing a T-shirt that said "I'm the Republican Barack warned you about." Hagmeier said he has long been a Republican, but he is turned off by the party's candidates this year and likes what he hears from Obama.

"He's talking about just being an American and furthering the cause of America," said Hagmeier, an industrial technician from Coralville.

A poll released Dec. 20 by Zogby International showed Obama beating GOP presidential contenders Mike Huckabee, Rudy Giuliani, Mitt Romney, John McCain and Fred Thompson. But other national polls have shown both Obama and Clinton beating some Republicans but not others.

Obama did not spell out where he thinks Edwards has flip-flopped since his 2004 vice presidential campaign, but in the past he has noted Edwards' vote for the resolution authorizing the Iraq war — a vote Edwards now says he regrets. Edwards also supported the "No Child Left Behind" initiative but now says it should be overhauled.

The Illinois senator also rejected arguments that he's too nice or too inexperienced to fight special interests in Washington. Obama said listening to other views and looking for common ground is not a sign of weakness.

People who say he needs more seasoning in Washington just want to "boil all the hope out of him" so he sounds just like everybody else, Obama said.

Later, at a stop in Ottumwa, Obama said his campaign won't be hurt by ads and mailings that claim his health-care plan won't ensure coverage for all Americans.

"Now in the closing days we're seeing the last tactics," he said. "They're starting to send in a whole bunch of money from undisclosed donors and they're starting to mail out stuff saying, 'Oh, Obama doesn't cover everybody in health care.'"

"This is what folks do when they want to stop change," Obama said. "And you know what? It's not going to work."