The Minnesota U.S. Senate race remains a tossup on the final weekend of the campaign, with the outcome likely to be decided by who can snatch away the most voters from third-party contender Dean Barkley.

A new Star Tribune Minnesota Poll shows DFLer Al Franken clinging to a slim lead over Republican Sen. Norm Coleman among likely voters, 42 percent to 38 percent. That's within the poll's 4.1 percentage point margin of sampling error.

Independence Party candidate Barkley, who held steady at 18 percent in the two previous Minnesota Polls, slipped three points to 15 percent.

The fluid nature of the contest is reflected in the results of a handful of polls the past week that reported results ranging from a six-point lead for Coleman to a five-point lead for Franken.

What this means is that after more than a year of exhaustive campaigning, a whopping $40 million spent and nonstop ads ranging from policy clashes to character attacks, it could be a last-minute development -- performances in tonight's final debate on Minnesota Public Radio, unusually heavy voter turnout or ongoing fallout from breaking controversies -- that determines the outcome.

In the past few days, Coleman has charged Franken with breaking the law by allegedly airing falsehoods in his ads. Meanwhile, the senator has faced questions about two lawsuits alleging that his wealthy friend transferred $75,000 to him from a Texas company through his wife's employer. Each candidate vehemently denies the respective accusations.

Both events came to light midway through the period that the poll was conducted, Wednesday through Friday.

The challenge now for Franken and Coleman is to draw the few remaining undecideds -- 4 percent of those surveyed -- and peel away enough votes from the sizable bloc commanded by Barkley, who launched his first and only TV ad last week.

Desirae Rhodes of Brainerd, a 24-year-old blackjack dealer at Grand Casino, said she doesn't like Coleman and has been leaning toward Franken -- "He's for the middle class, he wants to help the environment" -- but as of now is supporting Barkley.

"I don't know much about Barkley at all, but I know that he hasn't been running smear campaigns," said Rhodes, one of the poll respondents. "If you're going to bash the other opponent, are you a good candidate to vote for?"

While the poll shows that support for all three candidates is somewhat soft, Barkley's support is especially squishy. Only 27 percent of those supporting him said their support was strong, compared with 60 percent for Coleman and 54 percent for Franken.

According to the poll, Franken would have a six-point lead over Coleman if Barkley wasn't in the race.

Of the 933 likely voters polled, 37 percent said they considered themselves Democrats, 30 percent said they are Republicans and 30 percent called themselves independents.

According to the poll, Coleman has succeeded in persuading voters that he would be more effective in the Senate than Franken. But he remains unable to shed the tattered mantle of President Bush in which Franken has cloaked him; 61 percent still consider Coleman someone who usually follows Bush.

After a slump to 38 percent a month ago, Coleman's job-approval rating has bounced up to 44 percent among likely voters. But that's still in the danger zone for an incumbent.

Coleman enjoys a big lead among white evangelicals; 59 percent support him, compared with 28 percent for Franken and 10 percent for Barkley. Among voters who consider social issues most important, Coleman has a huge advantage over Franken, 81 percent to 15 percent.

Krysta Niznick, 29, a stay-at-home mother in Minneapolis, said she appreciates Coleman's "stand on pro-life and pro-family issues, and he's been consistently for that. I think that's a major issue. People need to look deeper than just the economy."

But Coleman has suffered more of a backlash from negative ads he's run. While a majority of poll respondents (63 percent) said that both campaigns had attacked unfairly, more (15 percent) said that only Coleman's attacks were unfair compared with those who said only Franken's attacks were unfair (9 percent).

Poll respondent Kevin Whiteford, 50, a correctional officer in Madison, said he's liked Franken "since his 'Saturday Night Live' days, and when I listen to him talk I feel like he'd do a better job for the state,"

Coleman does slightly better than Franken among independents: 35 percent say they support the senator, compared with 32 percent for Franken and 25 percent for Barkley.

Kevin Duchschere • 612-673-4455