June 9 (Bloomberg) -- Democrats see nothing standing in the way of big gains in November by picking up Republican-held U.S. Senate seats in states from New Mexico to North Carolina. Nothing, that is, except bawdy sexual humor and unpaid taxes.

With bright electoral prospects across the U.S., a dark cloud recently settled over Minnesota, where comedian and author Al Franken had been among Democrats' most promising challengers -- until recent flaps about delinquent taxes and a ribald Playboy magazine essay about make-believe sex robots.

Franken, 57, got over one hurdle June 7. After the former ``Saturday Night Live'' star apologized for making some voters uncomfortable, the Democratic-Farmer-Labor Party's state convention endorsed his bid to unseat first-term Republican Senator Norm Coleman. The curly-haired comic still must win a Sept. 9 primary, and some Democrats worry that more damaging off- color antics may surface.

``The Republicans are going to try to pull up anything they can,'' said convention delegate Joan Wittman, 77, of St. Paul. ``Unfortunately, Al's career may give them more material.''

Franken came under fire three weeks ago when Republicans circulated a 2000 Playboy article headlined ``Porn-O-Rama,'' in which Franken jokingly extolled computer technology's contributions to pornography and, in graphic detail, recounted imaginary sexual encounters with humans and a machine.

Joked About Rape

Minnesota politicians, including four-term Democratic U.S. Representative Betty McCollum, said Franken's article was vulgar and demeaning to women, and questioned whether he can win. The state Republican Party fed the controversy June 5, publicizing 13- year-old quotes in which Franken joked about rape while discussing a skit for NBC's ``Saturday Night Live.''

Franken said he regrets that his past work offended some voters, including feminists in his own party. Republicans are hand-picking a few items that don't reflect his views or his 32 years of marriage, Franken said in an interview.

``Most of the stuff I wrote was really funny and really appropriate, and some if it wasn't funny and wasn't appropriate,'' he said. ``I am sorry if what I did has caused some people to doubt my commitment to them on some issues.''

The Playboy controversy followed news in April that Franken spent $70,000 on back taxes and penalties in 17 states where he'd made paid appearances from 2003 to 2006. Franken blamed an accountant's mistake for delays in paying out-of-state taxes.

Sept. 9 Primary

Franken could still face 11th-hour opposition in the Sept. 9 primary or a third-party challenge in November, says Larry Jacobs, a political science professor at the University of Minnesota in Minneapolis. Coleman, 58, a former St. Paul mayor who squeaked into office in 2002 by 2 percentage points, may be vulnerable this year for supporting many of President George W. Bush's policies.

``Democrats in Minnesota are just pulling their hair out,'' Jacobs said. ``You've got an environment that's very favorable to Democrats and a Republican incumbent who's clearly vulnerable.''

Bush's slumping popularity, soaring gasoline prices, the Iraq war, and the prospect of recession at home give Democrats a chance to build on their slim 51-49 Senate majority. Republicans must defend 21 of the 33 Senate seats at stake in 2008.

``Democrats definitely have the wind at their back,'' said Jennifer Duffy, Senate editor of the nonpartisan Cook Political Report.

November Opportunities

November's races feature once-in-a-generation opportunities. Virginia Republican John Warner is retiring after 30 years in the Senate. The Democratic candidate, former Governor Mark Warner, who isn't related to the incumbent, had a 55-37 percent lead in a May Rasmussen poll over the Republican nominee, former Governor Jim Gilmore.

Pete Domenici, a New Mexico Republican, declined to seek re- election after 36 years in the Senate. U.S. Representative Steve Pearce won New Mexico's Republican Senate primary over fellow Representative Heather Wilson, who was considered the stronger general-election candidate, Duffy said. A Rasmussen poll last month showed Democratic U.S. Representative Tom Udall with a 53-37 percent lead over Pearce.

North Carolina Republican Senator Elizabeth Dole has seen her once-huge lead over Democratic state Senator Kay Hagan shrink to a competitive race. Democratic strategists see potential gains in at least a half-dozen other states.

Serious Money

After decades as a funnyman, Franken has shown he's a serious candidate, raising $9.4 million by the end of March compared to Coleman's $8.7 million. Franken said recent controversies will fade by fall, when the contest will turn on policy differences.

``Probably these things haven't been helpful, but I think it's a long time before the general election,'' he said.

In an interview, Coleman said he'll stress Franken's lack of experience. Coleman also may benefit from September's Republican National Convention at the Xcel Energy Center, which Coleman pushed to build as St. Paul mayor.

``At this point, I'd much rather be in my place than Al Franken's place,'' he said.

After the June 7 endorsement, Minnesota Republican Chairman Ron Carey said Franken's comedy will continue to provide political ammunition: ``Each and every DFL candidate on the ballot this year will need to explain why they refused to condemn Franken's demeaning and degrading comments that rob women of their dignity.''

To contact the reporters on this story: Laura Litvan in Rochester, Minnesota at llitvan@bloomberg.net

Last Updated: June 9, 2008 00:01 EDT