Franken is expected to have a much tougher time against the incumbent Republican nominee, Sen. Norm Coleman. In the primary, he paid little attention to Priscilla Faris, who labeled him a carpetbagger, the Minneapolis Star Tribune reported.
Coleman's only opposition was from a fugitive who is out of the country.
Dean Barkley, who served briefly in the Senate after being appointed by former Gov. Jesse Ventura, won a three-way race for the Independence Party nomination.
Franken, who grew up in Minnesota before attending Harvard and spending many years in New York, entered politics through books such as "Rush Limbaugh Is A Big Fat Idiot" that combined serious issues with often scatological humor.
Coleman began his political career in the Democratic Farmer Labor Party but switched to Republican. He won the Senate seat in 2002 after the incumbent, Paul Wellstone, a Democrat, was killed in a plane crash just before the election.