Psst, here's a tip about the Republican Primary in Michigan: You don't have to be a Republican to vote next Tuesday.

Lately some liberal commentators have been urging Democrats to take Michigan's status as an "open primary" state in an unusual direction: Vote for the candidate you may dislike the most (Rick Santorum) in order to help the candidate you really support (Barack Obama).

Some are calling this a dirty trick. Some say it could backfire for Democrats. And others doubt that such a sabotage tactic will play a meaningful role in the Michigan outcome.

But everyone agrees that Democrats and independents can play an important role in Michigan's Republican primary, as they account for perhaps 30 percent of all ballots cast. And if Mr. Santorum were to win Michigan, that would deal yet another big setback to the campaign of Mr. Romney, who is viewed in public opinion polls as the "most electable" of the potential Republican challengers to President Obama.

Here's how liberal blogger Markos Moulitsas publicized the case for what he calls "Operation Hilarity" a few days ago:

"It's time for those of us who live in open primary and caucus states – Michigan, North Dakota, Vermont and Tennessee in the next three weeks – to head out and cast a vote for Rick Santorum," he wrote on the Daily Kos website. "Why would we do such a crazy thing? Lots of great reasons!"

Among the reasons: Even if Romney ends up with the nomination, "the longer this thing drags out, the more unpopular the Republican presidential pretenders become," Mr. Moulitsas wrote. Mr. Obama's poll numbers, by contrast, have been rising as the GOP contest has become more tumultuous. And judging by recent primaries, even a relatively small number of votes can be decisive. ("Republican turnout ... appears to be getting worse by the contest," Moulitsas opines.)

Moulitsas and some others have amplified this message in the past few days, but political analysts say it's unlikely that this kind of get-out-the-vote effort will prove decisive in Michigan.

"Certainly some Democrats will try to vote for the weakest Republican who has a chance of being nominated," says Paul Abramson, a political scientist at Michigan State University in East Lansing. But those voters will be too few in number to tilt the outcome, he predicts. Far more likely, he says, is that the outcome will be affected by Democrats and independents who vote for the Republican candidate they like the best.

"That could be important," Abramson says. "I would guess that most of them will vote for Romney."

Currently, opinion polls show Santorum and Romney in a close race, with one week of campaigning (and advertising, in which Romney holds a financial edge) to go.

Whatever happens, the battle for Michigan is important.

The outcome will go a long way toward determining who is perceived to be gaining or losing momentum heading into "Super Tuesday," March 6, when 25 percent of all delegates to the GOP convention will be chosen in a single day. And Michigan is one of the biggest "swing states," appearing winnable by either party in 2012. The primary is thus a set-up with Michigan voters for a high-stakes November contest.

Arizona and Washington also have a primary vote or caucus between now and March 6, but Michigan is symbolically the most important, as a swing state and the place where Romney's father served as a popular governor.

Voters in Michigan can only cast a ballot in one primary, but Democrats there have little reason to care about voting in the primary of their own party. Obama stands as the clear nominee.

In recent Michigan polls, at least two-thirds of likely voters in the GOP primary are Repbublicans, while 5 to 18 percent have been Democrats and the rest independents or members of some other party.

Steve Mitchell, president of one of the polling firms, Mitchell Research & Communications, says he hasn't seen evidence of a rush by Democrats to support Santorum in order to prolong the race or to promote a "weak" candidate. But, he warns, "It's always hard to pick that up in the survey."

Twelve years ago, some Democrats did cast what Mr. Mitchell calls "mischief" votes in the Michigan Republican primary, seeking to embarrass Gov. John Engler (R) in his efforts to promote the candidacy of George W. Bush.

The promoters of things like "Operation Hilarity" should perhaps attach a cautionary warning, though.

Four years ago, some Republicans cast what political scientists call "strategic votes" in Democratic primaries, with some viewing Obama as a weaker nominee for Republicans to face than Hillary Rodham Clinton. Obama had little trouble winning the general election.

And in 1980, some Democrats promoted Ronald Reagan during the primary process, Mitchell says, arguing that Jimmy Carter would stand a better chance against him than against other potential rivals including George H.W. Bush.

The idea of supporting Santorum – a politician with outspoken views on controversial social issues ranging from gay marriage to abortion – is a tough sell with many liberals, even as a mere "strategic" move.

"We need to push back on Santorum, not propel him into perceived popularity," writes David Badash on the blog The New Civil Rights Movement.

Santorum showed a lead over Romney and other Republicans among both Democrats and independents who are likley to vote in the GOP primary, according to Mitchell's latest poll, conducted along with Rosetta Stone Communications on Feb. 20.

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But many remain undecided.

Among Democrats, 41 percent of likely GOP primary voters said they were undecided, 19 percent said they will support Santorum, 16 percent will support Romney, 13 percent will support Newt Gingrich, and 11 percent will support Ron Paul.