Memo to Minnesota voters:

Brace yourselves.

You are in the eye of one of the nation's most watched, most expensive and most competitive Senate races across the country.

Expect millions of dollars worth of heated, potentially nasty politics from now until Nov. 4.

"When all kinds of people are paying attention, it just gets uglier," said Jennifer Duffy, of the nonpartisan, Washington-based Cook Political Report. "I've just had both parties say to me, 'We think this is the nastiest race of the cycle.' "

And the competition has really just started.

Already this month, Republican Sen. Norm Coleman, who formally announced his re-election campaign Wednesday, has said his likely opponent, Democrat Al Franken, has an angry, expletive-spewing, belittling history. In a fundraising letter Friday, his campaign called Franken a "celebrity millionaire using a statewide office for his own whimsical ideas."

Franken has said Coleman was a rubber stamp for special interests who have attacked Franken in an attempt to distract from the senator's record in Washington. And the Democratic-Farmer-Labor Party has criticized Coleman for his "shadowy supporters" who politicized "the tragic I-35W bridge collapse" for the senator's benefit.

Meanwhile, political bloggers are working to dig up dirt on the candidates, partisan trackers are following the candidates' moves and outside groups have begun spending money on television ads for the Senate race.

That's because Minnesota's race is at the center of a political tornado.

-- Coleman, a first-term senator, is considered one of the most vulnerable Republican senators up for re-election.

The political environment doesn't favor his party, and he narrowly won election in 2002 in highly unusual circumstances — Democratic Sen. Paul Wellstone's plane crashed 11 days before the election, and former Vice President Walter Mondale jumped into the race five days before Election Day.

But Coleman's a smart, charismatic campaigner who has proved his ability to sway Minnesota.

-- Franken, who made his name as a comedy writer and by presenting himself as a Democratic alternative to Rush Limbaugh, has a history of saying and doing things as part of his act that would make many Minnesotans blanch. Republicans have long delighted in the passages and recordings Franken's history has offered them.

But he's earned respect and credibility for running a serious, well-organized campaign, which, so far, hasn't been ruined by opponents trotting out Franken's past for more than a year.

-- Thanks to the fundraising prowess of both candidates — and the nation's attention to the contest — there will be money galore for the race. And, in politics, money to be spent often means mud to be slung.

"I think by October, a bathtub is the only thing you'll be able to turn on without hearing Norm Coleman and Al Franken attack each other," Tom Horner, a former Republican strategist, told the Associated Press.

But a few factors could mitigate the attacks.

Franken and Coleman and their campaigns have said recently that they'd like the race to be based on contrasts and issues — not mudslinging.

"In the end, I'll do the best I can," Coleman said. "I'll try to be positive and optimistic. I'll draw contrasts, but I think legitimate contrasts, not personal aspersions."

Franken, for his part, said his goal is to "hold Norm Coleman accountable for what he's done in the U.S. Senate" and the work he's done — and hasn't done — on health care, economic justice, the war in Iraq and other issues.

The campaigns of both men have reason to keep the race from deteriorating too badly.

Franken will have to work hard to give lie to the claims that he is an angry pit bull unsuited to the Senate; Coleman will have to keep high-minded if he wants those claims to stick.

And there is a thin chance the entire race could change dramatically the first weekend in June.

That's when DFL activists will meet in Rochester to officially nominate the party's Senate candidate.

While Franken is the strong favorite, University of St. Thomas professor and peace activist Jack Nelson-Pallmeyer is also a contender for the party's nod. 

"We are definitely still behind, but we are definitely gaining ground," Nelson-Pallmeyer said Saturday as he drove to a DFL convention in Madison, Minn. "There's still two and a half months before the endorsing convention. We're not going to catch up with Al on the money front, but I think we can catch up on the delegate front."

If delegates select him, his campaign would give the race a distinctly different flavor.

"One of the things I teach is conflict resolution," he said. "I really believe that this is not a time for more divisive politics. I think it is time that we come together."

Democrats Dick Franson and Darryl Stanton also have declared their candidacy for the Senate. Neither is running a widespread, statewide campaign.