Asked to describe his attitude in his last few months in office, Sen. Mark Dayton cited a line from the 1960s song "Me and Bobby McGee." "Freedom's just another word for nothing left to lose," he says.

The first-term Minnesota Democrat is not seeking re-election and, these days, sounds very much like a politician with little to lose.

In February, upset about a plan by a South Dakota railroad to run coal trains close to the Mayo Clinic in Rochester, Dayton said the clinic "is worth a hell of a lot more than the whole state of South Dakota."

He later apologized for the remark.

The following month, he called fellow Democratic Sen. Russ Feingold's proposal to censure President Bush over a warrantless surveillance program "an overreaching step by someone who is grandstanding and running for president at the expense of his own party and his own country."

Dayton did not apologize for that.

He even told a Minnesota high school group he'd give himself an "F" if he had to grade his accomplishments in the Senate.

"And I would give the entire Congress, of which I'm a member, an F for results," Dayton said in an interview. He pointed out that he also told the students he'd give himself an "A-minus" for effort.

Dayton, 59, announced last year that he would not seek re-election, concluding that Democrats could field a stronger candidate.

His reputation took a beating months earlier when he temporarily closed his Senate office, citing a secret intelligence report that he said made him fear for his staff's safety.

Dayton said he still takes his position seriously, "but the fact that I'm not up for re-election, every word is not going to be politically dissected, gives me a certain freedom that I haven't felt before."

"I didn't just say, 'Well, I'm not going to run,' so now this light switch or something turned on," Dayton said. "But it's sort of evolving."

He said he's felt more relaxed without the pressures of raising money and having a "political target on my back."

"Mark Dayton is in his last months in public office, probably ever," said Larry J. Sabato, director of the University of Virginia's Center for Politics. "He hasn't had a particularly successful tenure. So why not speak out as bluntly as possible and have some fun?"

Still, said Steve Schier, a political science professor at Carleton College in Northfield, Minn., "giving himself an F — that must be a first in Senate history."

"This is a fellow who's issuing a few Bronx cheers on the way out the door," Schier said.

The Minnesota Republican Party has noticed Dayton's increased bluntness with approval.

"He's certainly let it rip lately," said Mark Drake, the party's spokesman. "We appreciate his candor when he does acknowledge that he does deserve a failing grade for his performance in the Senate. I think he's right when he says he's been ineffective and hasn't accomplished a lot."

Dayton stressed that while he's speaking his mind more freely, he's no second-semester senior.

"I'm not coasting to the conclusion of this job," he said. "I am fully engaged."

Dayton doesn't have to worry about post-Senate employment. He's a multimillionaire, and has been donating his $165,200 Senate salary to the Minnesota Senior Federation.