The Minneapolis Star Tribune reports that Al Franken will run for the U.S. Senate in 2008 - and the author of Rush Limbaugh Is a Big Fat Idiot wants to be taken seriously.

The comedian and liberal talk-show host declared his candidacy Wednesday for the Minnesota seat currently held by Republican Norm Coleman.

His decision guarantees that the 2008 race will be more entertaining than usual and closely followed by national media.

Franken immediately confronted the central question he will face in the early going - whether a life-long comic should be taken seriously.

“Minnesotans have a right to be skeptical about whether I’m ready for this challenge and to wonder how seriously I would take the responsibility that I’m asking you to give me,” Franken said in a video message on his campaign website, launched at 1 p.m.

“I want you to know: nothing means more to me than making government work better for the working families of this state. Over the next 20 months I look forward to proving to you that I take these issues seriously.”

Offering personal stories about his childhood in Minnesota and about how his father and other family members were able to survive and thrive with the help of federal education and Social Security programs, Franken said the government should “have your back.”

“That should be our mission in Washington, the one FDR gave us during another challenging time: freedom from fear.”

Franken’s announcement came on the final day of his show on the liberal radio network Air America. His decision instantly makes him a serious contender and brings national attention to the race.

According to the Washington Post, Franken announced a few weeks ago he would leave Air America, tellng prominent Democrats off the record about his plans to seek office.

His name is well-known, and Al Franken is likely to be well-funded, but he’s expected to be challenged by several other Democrats, including wealthy trial attorney Mike Ciresi.

His candidacy will also test whether Minnesotans are in the mood for another celebrity-turned-politician, after the 1999-2003 governorship of former WWE wrestling star Jesse Ventura.

Ventura ascended to the office as an outsider and a uniter, but his fame and occasionally outrageous behavior regularly brought national attention to the state in a negative way, and tried the patience of many Minnesota residents.

Stephen Hess, a professor of political science at George Washington University, said Franken’s bid is serious.

“He’s not doing this as some folks have done it to give them better gigs on the Borscht circuit.”

Coleman is viewed as vulnerable because of recent Democratic resurgence in Minnesota and President George W. Bush’s unpopularity. But his proven skills as a campaigner and fundraiser make him a formidable opponent.

Minnesota Republican Party Chairman Ron Carey issued a statement saying Franken offers “nothing but polarization and vitriolic personal attacks.”

Franken, 55, was born in New York City but grew up in the Minneapolis suburb of St. Louis Park. He graduated from Harvard in 1973, and in 1975 joined the writing staff of Saturday Night Live during its first season.

He soon began appearing in sketches and remained a fixture on the show well into the 1990s. In 1996, Franken took his career in a political direction when he wrote Rush Limbaugh Is a Big Fat Idiot and Other Observations.

He’s since published several other books critical of Republicans. In his latest effort, The Truth (with jokes), Franken criticized Coleman for his leadership of the Permanent Subcommittee on Investigations, saying that Coleman had not held a single hearing on Iraq war corruption.

In 2005, Franken and his wife moved back to the Twin Cities, which was widely interpreted as laying the groundwork for a campaign.