MINNEAPOLIS - For someone who has never held nor run for office, comedian Al Franken enters Minnesota's Senate race with an unusually rich and public record - a gold mine of political fodder Republicans are eager to exploit.

Opposition researchers are already scouring more than a half-dozen books, thousands of radio show hours and years of edgy television footage for provocative, caustic and off-color Franken statements they can use against him in campaign ads.

"He's a researcher's dream because he's made so many outrageous statements," said Minnesota Republican Party chairman Ron Carey. "Running for the United States Senate is not about comedy, it's about common ground."

Therein lies the challenge for Franken: Defending outlandish things from his days on the humor circuit as he presents himself to voters as a composed, capable alternative to Republican Sen. Norm Coleman in 2008.

Within hours of his campaign announcement, Republicans circulated pages of colorful quotes from Franken interviews and books. GOP bloggers trotted out a "Saturday Night Live" skit he co-wrote where rogue cops killed two lesbians, suggesting Franken was promoting gay bashing.

Franken expects his foes to try to take his past out of context and "give it a sinister spin." He doesn't see it as a liability.

"Minnesotans really know that a joke is a joke," he said in an interview. "I think they know what exaggeration is. I think they know hyperbole. I think they know what irony is."

Franken, expected to first face other Democrats vying to take on Coleman, began the transition from freewheeling commentator to aspiring senator on Thursday with a visit to a Minneapolis clinic that provides medical care to uninsured patients.

Franken toured the clinic with its volunteer doctors, who do everything from dental work to mental health counseling. The visit gave Franken a platform to stake out a goal of universal health care, although he didn't offer a formula for getting the country there.

Dressed in a dark business suit, Franken asked many questions and took lots of notes. And, naturally, he fell back on humor, laughing and joking with a young woman getting her teeth whitened.

"I've never had my teeth whitened. Probably now that I'm a candidate I should do it," he said.

He dove into other topics at a news conference just down the street at the comedy theater where he got his start decades ago.

He promoted an Apollo-style program for renewable fuels, dramatically increasing the country's commitment to power from wind, water and crops. He talked of cracking down on employers who hire illegal immigrants.

He spoke authoritatively about Iraq, leaning on firsthand accounts from his four trips there and interviews he conducted with military leaders and other experts during his now-ended radio show on Air America.

But even on that topic he couldn't resist levity when talking about moving U.S. troops from Baghdad to more stable regions of the country, such as Kurdistan in the north.

"They don't hate us, the Kurds," Franken said. "Sixty percent of Iraqis say it's OK to kill Americans. The Kurds are like only 10 percent."

Franken said he doesn't plan to change his style now that he's a candidate.

"I can't afford to be something I'm not. I have to be myself," he said. "Humor and seriousness are not in opposition to each other.

How Franken mixes humor with serious issues and how opponents try to use his loose tongue against him will loom large in the campaign, said Rutgers University political scientist Richard Lau.

"The question is will he turn off some Democratic voters or will they be worried about him," Lau said. "How will his candidacy lie with the independent voters?"

Another expert on political rhetoric said Franken's rivals have to be careful about making hay out of things obviously said in jest or they'll be chided for lacking a sense of humor.

"He might do well to make his candor and his irreverence an asset," said Marty Kaplan, associate dean at the University of Southern California's Annenberg School for Communication. "You want straight talk, here's straight talk."

(Brian Bakst has covered Minnesota politics for the Associated Press since 1999.)