“Minnesotans know what’s a joke and what isn’t,” Mr. Franken said in an interview in jeans, a T-shirt and sweat socks at the Minneapolis town house he bought when he moved here from New York in 2005.

“There’s not necessarily a contradiction certainly between satire and being serious,” he continued. “To me they’ve always been part and parcel of the same thing. What a satirist does is looks at a situation, finds the inconsistencies, hypocrisies, absurdities, and cuts through all the baloney and gets to the truth. That’s pretty good training, I think, for the United States Senate.”

Minnesota has made unorthodox political choices before. In 1998, voters chose Jesse Ventura, a third-party candidate and former professional wrestler, for governor, although some here suggest that the experience  Mr. Ventura left after one term  might have left them less willing to try something different again.

Mr. Franken has shown that he is so far the most formidable fund-raiser among the Democratic hopefuls. (And in the most recent quarter, at least, the $1.89 million he raised was on par with Mr. Coleman’s $1.7 million.)

Some Republicans even hope to see him win the Democratic endorsement. With Mr. Franken’s long trail of Stuart Smalley affirmations, Air America broadcasts and books with names like “Lies and the Lying Liars Who Tell Them: A Fair and Balanced Look at the Right” and “Rush Limbaugh Is a Big Fat Idiot and Other Observations,” he would make a tempting, target.

“The question on the minds of many Democrats now is whether a Franken candidacy is going to lead to a campaign in which the challenger’s record rather than the incumbent’s will be the subject of the campaign,” said Lawrence Jacobs, a political scientist at the University of Minnesota.

While polls show that Minnesotans mostly know who Mr. Franken is, his critics say many of them may not like what they know.