The Iowa caucuses have the potential to transform the presidential race in a single stroke, launching one candidate on a path to the White House and sending others into political oblivion.

Or not.

That uncertainty reflects the incredibly fluid nature of the Republican campaign (four of 10 Iowans telling pollsters they could still change their minds—what’s wrong with these people?). But it also highlights a less-than-overwhelming field (Rick Santorum is now a powerhouse?); the bizarre nature of the caucus process (freeze your butt off going to meetings that choose no delegates); and the vast terrain for media interpretation (sure, we’re overbearing, but we’re inescapable—deal with it).

After all, Politico’s Roger Simon has already anointed Mitt Romney as the winner whether he finishes first, second, or third. Talk about spoiling our fun.

So what’s a normal American—that is, one who’s spent the last two days more focused on bowl games than tracking polls—supposed to do?

Here’s a handy guide to the contenders and where they stand heading into Tuesday night’s voting.

Mitt Romney. At the beginning of 2011, the conventional wisdom was that when the dust settled, Romney would win the GOP nomination. At the beginning of 2012, the CW is that Romney will win the GOP nomination. It’s like last year’s stock market: lots of volatile swings, but it ended right back where it started.

If Romney takes Iowa, there’s no reason in the world he shouldn’t win New Hampshire, where he has a vacation home, next Tuesday. And if that happens, this contest is effectively over and we’re in for months of excruciating boredom, notwithstanding the inevitable chatter about late-starting insurgents and Donald Trump and a brokered convention.

If Romney places second behind Ron Paul, that’s almost as good, since not many outside the congressman’s immediate family believe he can win the nomination, but he could stymie others in the anyone-but-Romney crowd. A third-place finish could hurt Romney, but he’s got the money and organization for a long fight—and by any standard is a more disciplined candidate than in 2008.

Not bad for a formerly moderate Massachusetts governor who spent little time in Iowa and has endured endless abuse for being deadly dull (though he did manage to appear “with it,” as the kids say, by likening Barack Obama to Kim Kardashian).

The problem for Rick Santorum is that he’s got no money, which will make it difficult for him to replicate an Iowa success.

Rick Santorum. He was a lonely figure on the trail all year, sadly surgeless as outsiders such as Herman Cain soared to the top of the polls before flaming out. But Santorum, who laid the groundwork by visiting Iowa counties that most reporters couldn’t find without a GPS, is having a strong stretch run.

If he wins, he’s on the cover of Newsweek. (That’s my recommendation, anyway, though it didn’t do much for Michele Bachmann after she won the Ames Straw Poll.) If he finishes a solid second or third, the media will grant him the mantle of Serious Candidate (yes, the same media that wouldn’t give him the time of day all year and barely asked him any questions in the debates).

The problem for Santorum is that he’s got no money, which will make it difficult for him to replicate an Iowa success, even in conservative South Carolina, which like Iowa has a strong evangelical vote. He won’t have the time to visit every coffee shop clad in a sweater vest. Plus, while he brags about winning elections in the blue state of Pennsylvania, the inconvenient fact is that he got clobbered by 18 points when he tried to hang onto his Senate seat in 2006.

Santorum has his strengths. He’s earnest, has blue-collar roots, and is an unabashed social conservative. But since he emerged as a threat in Iowa about 12 minutes ago, he hasn’t faced withering attacks from opponents or the inevitable media scrutiny of his record (folks might be reminded that in 2003 he attacked the right of gays to have consensual sex while allowing it wasn’t quite in the category of “man on dog” sex). Without much cash in the bank, Santorum would be vulnerable to an avalanche of negative ads.

Newt Gingrich. Speaking of such an avalanche, it seems to have all but buried the former speaker’s chances in Iowa. His December surge was remarkable, given all the baggage that Gingrich carries from his erratic tenure as House leader in the 1990s and his three marriages—not to mention the way his campaign essentially imploded last summer. (His recent explanation that he visited Greece with Callista in the heat of the campaign to prompt his consultants to resign sounds like a bit of revisionist history.) Once Gingrich was leading the polls, the pundits began betting whether he would self-destruct. But it was his inability to respond to nearly $3 million in attack ads from a pro-Romney PAC—except to whine about it, which isn’t much of a message—that knocked him back to earth.

Gingrich is banking on a respectable enough finish that he can stay alive for the other January contests. If he winds up, say, in fifth place, it will be nearly impossible for him to recapture his earlier momentum. Newt is an ideas man who is seen by many Republicans as having the stature to be president. But his stubborn insistence on staying positive as Romney’s allies bombarded him in Iowa (while Romney purported to take the high road) may have sealed his fate. “I can’t do modern politics,” Gingrich lamented the other day, and the caucuses could prove him right.

Ron Paul. In a sense, he’s already won Iowa. Four years ago, he finished fifth in the caucuses with 10 percent of the vote. Now he’s on track to at least double that. The 76-year-old Texas congressman even felt confident enough to go home for New Year’s weekend. Or maybe he was just tired.

Despite a litany of positions that many people would regard as fringe—abolish the IRS, abolish the income tax, pull U.S. troops from Germany and South Korea and just about everywhere else—Paul was probably on track to win the caucuses. But he may have peaked a moment too soon, allowing the media to rediscover the racist filth published in his old newsletters (which he says he never saw) and the controversial passages in his 2007 book (those afflicted with AIDS are victims of their own lifestyle; people who suffer sexual harassment at work should just quit).

Paul’s cranky libertarianism has its appeal, especially to a certain segment of young people, and even a second-place finish in Iowa would be quite an accomplishment. Still, it’s hard to see where he goes from there. Paul is nowhere in New Hampshire, there’s a natural ceiling on his vote, and what’s left of the GOP establishment is horrified by his foreign-policy views. Iowa may be as good as it gets for Ron Paul.

Rick Perry. The Texas governor is playing for respectability now. If he finishes fourth or fifth, he may be able to keep limping along, but it is hard to imagine him again becoming a credible threat to win the nomination.

Perry never got a second chance to make a first impression. He and his team, schooled in the cowboy politics of the Lone Star State, were unprepared for the crazed intensity of a national campaign, and Perry’s spectacular debate flops sealed the deal. By the time he steadied himself, too many voters had concluded that he wasn’t ready for the presidency, intellectually or stylistically, and fundraising slowed to a trickle. Iowa may not be Perry’s swan song, but the band is warming up.

Michele Bachmann. The congresswoman’s challenge was always to become the top choice of evangelical voters, besting Paul and Santorum, and thus position herself as the conservative alternative to Romney. She failed for a variety of reasons, as exemplified by last week’s embarrassing defection of her Iowa chairman to the Paul camp.

An experienced legislator, Bachmann failed to broaden her message during her brief moment in the spotlight, repeating her standard lines about killing Obamacare and making its author a one-term president. She clashed with her advisers, struggled with a bare-bones operation, and made several high-profile flubs, including repeating a woman’s claims that a cancer vaccine caused mental retardation. Bachmann, who was born in Iowa, seemed to fade in the later debates, and her slide in the polls reinforced the notion that she had blown her big chance. Perhaps the fact that Iowa has never sent a woman to Congress or the governor’s mansion was a factor as well.

While she’s vowing to hang on, as they all do, a poor finish will likely spell the end of Bachmann’s campaign and force her to focus on saving her House seat in Minnesota.

Jon Huntsman. Who?

The former Utah governor abandoned Iowa to put all his chips on New Hampshire, where he now says he will use some of his personal wealth after vowing not to do so. If Huntsman doesn’t break out of single digits in the Granite State, he’s toast. Perhaps the enduring mystery is why someone who has gotten so much respectful attention from the pundits could never establish a connection with the only people who ultimately matter: the voters.

Now you can sit back, wait for the caucus results, and see how many of the prognostications turn out to be wrong.