In less than a week, the Iowa caucuses will crown the first winner in the race for the GOP presidential nomination.

But there’s no guarantee the victor will become the nominee.

Polling has been all over the place in this contest, and evangelical voters — the biggest voting bloc of the caucuses — have yet to coalesce behind a conservative candidate.

One of the front-runners could take the crown or one of the lesser-known contenders could mount a come-from-behind victory.

Either way, Jan. 3 marks a turning point in the race.

Here’s what’s at stake for each of the Republican candidates:

Rick Santorum:

He’s involved in a hotly-contested sub-primary right now — a battle with Michele BachmannMichele Marie BachmannBachmann won't run for Franken's Senate seat because she did not hear a 'call from God' Billboard from ‘God’ tells Michele Bachmann not to run for Senate Pawlenty opts out of Senate run in Minnesota MORE to become the candidate of choice among social-conservative die-hards.

For most of the year, Bachmann has doubled or tripled the former Pennsylvania senator’s support in the state, but recent polling shows them, effectively, tied. More importantly, Santorum has had a late surge of momentum, buttressed by key endorsements, and is well-organized for the caucuses.

This will be the first and most important test, because Iowa’s evangelical-heavy caucus-goers will effectively weed out either Bachmann or Santorum.

If Santorum finishes ahead of Bachmann, he can credibly claim that he’s the undisputed voice of social conservatism. That probably won’t be enough to win the nomination or compete strongly in the ensuing primaries and caucuses, but it will keep him relevant and help him survive another month.

Michele Bachmann:

The Minnesota lawmaker's story is similar to Santorum’s, except there’s a slight complication for Bachmann. As an elected representative, she has to think about how continuing this presidential run affects her current job.

When Bachmann was surging this summer, it seemed she’d earned credibility as a major player on the national stage, but a series of gaffes, organizational confusion and campaign incompetence has left her looking like a relative amateur who jumped before she grew legs.

For Bachmann, there’s quite a bit of credibility at stake, and it can be argued that it will either help truncate or extend her primary.

If she finishes behind Santorum, she’s all but done as a credible challenger and risks going back to her district and another congressional election as a flame-out and, perhaps, an embarrassing one at that.

That alone might cause her to push on and try to regain some of her magic. But pressing on will be difficult, considering that her fundraising has been flagging, and would suffer even more if she finishes behind Santorum.

If she beats Santorum, though, she can claim the same thing Santorum is running for — a spot as the most vocal social conservative. The momentum from a moral victory over Santorum could carry her through the next month.

Rick Perry:

Rick Perry, and anyone else’s, lone shot is to become the anti-Mitt Romney. As such, he doesn’t need to win Iowa — he just needs to perform well enough relative to Newt Gingrich that he can make the case that he’s the most legitimate alternative to the former Massachusetts governor.

That’s doable for a few reasons. First, Gingrich has been falling in polls, even as Perry has been on the uptick. In November, Perry only cracked double-digits in one Iowa poll. In December, he’s done it in six straight surveys.

Second, he’s already faced the entire kitchen sink of attacks from his opponents. It nearly felled him, but he survived. Gingrich, on the other hand, is a fresh target, and between his opponents’ daily attacks, his lack of money and his discipline problems, it’s easy to see him crater again.

If Perry can beat Gingrich in Iowa, or at least over-perform expectations, he’ll probably skip New Hampshire and head to South Carolina to make his original case — that he’s mainstream enough to get establishment Republicans and conservative enough to win Tea Party-ers.

Newt Gingrich:

He’s got to staunch the bleeding. After holding double-digit leads in November, he’s fallen to third place this month. A Gingrich path depended on momentum from Iowa, survival in New Hampshire and a definitive victory in South Carolina. But Gingrich’s coalition is quickly falling apart. Tea Party conservatives have lost much of their trust in him, the establishment has firmly backed Romney, and social conservatives are uneasy with his personal baggage.

Gingrich has to finish in the top three to remain a top contender. No one expects Ron Paul to have a prayer in the nomination fight, so if Gingrich loses to only Paul and Romney, he can still come out of Iowa as the Romney alternative.

But if he falls to fourth, every story will focus on his falling star — much like those that have plagued both Bachmann and Perry this fall.

Gingrich probably won’t drop out no matter how poorly he does in Iowa and no matter how troubled his bid becomes.

With a bad finish, money will dry up, but he can begin distending his make-shift organization and become a rogue candidate again — showing up for debates and cable news hits, while falling further and further behind in the delegate count.

Mitt Romney:

Ironically, Iowa, where his bid started falling apart in 2008, might be the state that solidifies his lead as front-runner and the de facto nominee.

Romney is in second place in the Real Clear Politics average of state polling, but he’s lowered expectations so dramatically by largely avoiding Iowa that anything from a first- to third-place finish would be a win for him.

And, in another fortuitous irony, his dismal performance in 2008 has led to the conventional wisdom that he can’t win there and is ill-suited to play strongly. But he has an outside shot at winning, according to polls. A fourth place finish, meanwhile, would be survivable, especially with the New Hampshire primary one week later.

In short, anything between first and third place would be a win for him, and fourth place would hardly be devastating. He’s in better shape now than he ever was in 2008.

Ron Paul:

It’s not immediately clear how deeply the barrage of recent attacks on Paul will affect him in the caucuses.

Of all the candidates, Paul’s base is most committed and, therefore, least likely to be moved by the onslaught.

Still, part of Paul’s expanded support comes from Iowa’s significant evangelical population. That’s helping him move up in the polls, but there’s also the possibility that these newer Paul supporters will be turned off by some of his extreme moves on both foreign and fiscal policy.

If he wins Iowa, he’ll feed off one week of nationwide attention that will probably collapse once New Hampshire comes around. But regardless, his campaign will continue on. He’s one of the stronger fundraisers in the race — thanks to his rabid grassroots support — and will continue being a voice, if not a victor, in the primaries to come.

Jon Huntsman:

He’s boycotting the state caucuses, and isn’t expected to perform well. Not just because of the boycott, but mainly because of campaign missteps that pitched him as a moderate to liberal Republican.

He’s currently last in Iowa polling, but that’s OK. No matter how poorly he does, he’ll stay in the race at least until New Hampshire — the state on which he’s pinned all his hopes.