The big huddle begins promptly at 8 p.m. ET with results to follow by 10, hopefully. We’ll get “entrance poll” results at some point too, so don’t wander off. I’m less interested tonight in who wins the caucuses, actually, than who wins the death struggle between Perry and Gingrich to become the “electable” conservative Not Romney in South Carolina. (Why can’t Santorum be the electable conservative Not Romney again?) The loser of that arm-wrestling match is all but done, as is Bachmann. Perry should beat Newt: He’s spent way more in the state than Gingrich has and is set to make an impressive show of organizational muscle by turning out lots of precinct captains. Some of his fans have been insisting on Twitter, in fact, that he’s going to surprise Paul or Santorum and end up finishing third. (Perry himself is confident enough that he’s begun buying airtime in SC.) I’m skeptical, but if that happens, it’ll be big news tomorrow as a bona fide election-night surprise.

And really, that’s all we’re watching for tonight: Surprises. If, as expected, the top three are Romney, Paul, and Santorum then it doesn’t much matter in which order they finish. As long as Romney’s within a few points of first place, he’ll probably go on to steamroll everyone in New Hampshire. If he finishes a distant second or third, well, that’s a surprise and that’ll be the storyline for the next week. If Perry or Gingrich breaks into the top three, that’s a surprise and another major storyline ahead of South Carolina. Problem is, I don’t see how either of them does that. Santorum’s the social con who’s been surging and nothing’s happened in the past 48 hours that might change that. Paul’s taken damage from the coverage of his newsletters so he’s more likely to underperform, but it’s hard to imagine his supporters would come this far to let him down now. Figure he’s got a solid 12-15 percent who are willing to turn out for him even in a Category Five hurricane; he’s also got a terrific organization bent on turning out another 10-12 percent of disaffected Democrats, curious independents, and none-of-the-above Republican protest voters. I can’t believe he won’t crack 20 percent, and I also can’t believe that Perry will. My prediction: Santorum 27, Romney 24, Paul 21, Perry 13, Gingrich 10, Bachmann 5.

Here’s your dandy Hot Air/Townhall Twitter widget. I’ll be updating this post too with whatever tea leaves I can scrounge up on the wires, so don’t be stingy with the refresh button. To follow the results, I recommend two interactive state maps: One at the Des Moines Register and the other at Google. Confused about which counties matter and why? No worries, we’ve got cheat sheets for that too. Try the Iowa Republican and Politico. WaPo also has an interesting scorecard that attempts to set county-by-county goals for Romney based on his 2008 showing. That might be useful at a glance later to gauge whether he’s over- or underperforming.

Odds of anything happening tonight that resembles an encouraging outcome: Nearly zero. Stand by for updates, needless to say.

Update: Howard Fineman sums up Romney’s strategy this way: “Mitt showing off his savage machinery to GOPers as a reason to vote for him: Don’t vote for me, vote for the weaponry I will use on Obama.”

Update: Here’s Chris Matthews, whose candidate of choice will spend upwards of a billion dollars next year, comparing Romney’s attack ads against Gingrich to … the bombing of Dresden. Click the image to watch.

Update: Patrick Ishmael sends along the results of today’s HA reader survey. After roughly 3,000 responses: Perry 27.38% Gingrich 22.88% Romney 18.72% Santorum 17.46% Paul 6.58% Bachmann 4.94%.

Update: Ten minutes until caucus time and a friend points out that Romney’s odds on InTrade of winning Iowa have dropped to a shade above 40 percent. He was above 50 percent earlier today. Hmmmm.

Update: Bad news for Perry fans: According to the entrance poll, it is indeed a three-way race between Romney, Santorum, and Ron Paul.

Update: Food for thought: If you’re hoping for a brokered convention, what’s the optimal result tonight? Probably Santorum, Paul, and Romney in that order, no? Paul will fight on no matter what, but Santorum needs major encouragement to make it and keep it a three-way race.

Update: Take a look at what’ll be running in New Hampshire’s most influential paper tomorrow.

Update: The entrance poll has it Paul 24, Romney 24, Santorum 18, but Huckabee ended up far outperforming his entrance-poll numbers on caucus night 2008. More from the Hill:

As expected, Paul polled best with younger voters, garnering more than half of the support of voters under 29 and a plurality of those aged 30-44. Romney, meanwhile, led the field among voters over 45.

Paul also led with nearly four-in-ten voters who had never before attended a GOP caucus, while Romney earned the vote of nearly three-in-ten previous caucusgoers. The 71 percent of those surveyed who called themselves Republicans broke more for Romney than any other candidate, while almost half of self-described Independent voters went for Paul.

Santorum, meanwhile, earned more than a quarter of those who self-identified as very conservative, and led among voters who said they “strongly support” the Tea Party. Moderates and liberals were most likely to vote for Paul.

According to Zach Wolf of ABC, fully six in 10 Ron Paul supporters don’t identify as Republican. He’s apparently cleaning up among independents, as expected — and they’re turning out in higher than usual numbers.

Update: Hearing on Twitter that Fox News expects Bachmann, the Ames straw poll winner, to finish last based on the entrance poll. That’s the end of her campaign, and probably the end of Ames being taken even remotely seriously.

Update: It’s early but still interesting: As of 8:50 ET, the Google map I linked above shows Paul at 24 percent, Santorum at 24 percent, and Romney at 22 percent, all of which is in line with entrance polls. Surprisingly, though, Newt is fourth with 13 percent; Perry trails with 10. Here’s Perry’s precinct speech tonight, which was good on the merits but not good enough to push him into the top tier.

Update: According to Jake Tapper, the Paul campaign is taunting Huntsman:

@RonPaul tweeted then deleted 2 Huntsman “we found your one Iowa voter, he’s in Linn precinct 5 you might want to call him and say thanks”

Update: Says Chuck Todd, “Every model our elex team has indicates as little as .3% separates 1st and 3rd.” You know who this benefits?

Update: Come and get it: CNN has published full crosstabs for the Iowa entrance poll.

Update: If you’d rather follow statewide totals instead of county-by-county, CBS has you covered. As of this writing, with 270 precincts reporting, Paul leads Romney by roughly 120 votes.

Update: As of 9:28, with 433 precincts reporting, here’s the CBS vote count. No joke:

Rick Santorum 6,067
Mitt Romney 6,060
Ron Paul 6,018

The margin between first and third is 49 votes. Remind me again: Now that we know who the top three will be and that it’ll be very close, what does it matter what the order is? If Romney finishes third, that’ll be good enough for a tepid “is Romney underperforming?” narrative this week, but it does nothing to answer the question of who’s supposed to emerge from the field and beat him in the long slog to the convention.

Update: At 9:39 ET, with almost a third of all precincts reporting, Gingrich leads Perry by slightly more than a thousand votes. That doesn’t sound like much in the abstract, but remember that this is a small pool of voters; right now, Romney leads with a little over 7,800 votes total. Starting to look like Newt will be fourth place, which means Perry’s on life support.

Update: Nate Silver knows who this benefits — and it isn’t necessarily Romney:

In particular, Mr. Huntsman might be hoping for a highly ambiguous finish, especially an effective three-way tie as is projected by the current polling, and which would leave no candidate with demonstrable momentum. That would free up news bandwidth for him in New Hampshire, where his polling is stronger but where he will have to compete with several other candidates for attention. The less news coming out of Iowa, the more time the news media will have to speculate about whether it is finally Mr. Huntsman’s turn to surge.

Update: An actual tweet from Buddy Roemer: “Hermain Cain is currently beating me in Iowa. #seriously”

Update: Lefty Ari Melber: “THIS is the key data: It’s not a 3-way race among self-identified Republicans: 28% for Santorum, 27% for Romney, 14% for Paul & Gingrich”

Update: Someone on Twitter points out that Romney’s on pace at the moment to do slightly worse in Iowa than he did in 2008. In a way, that’s apples and oranges — he invested more time and money in the state then versus now. But still: 23 percent. The 23 percent juggernaut. Says Dan McLaughlin, “Just imagine if anyone had run negative TV ads vs him.”

Update: At 10:05 ET, things are starting to shake out. Romney and Santorum are neck and neck with just 110 or so votes separating them, but Paul has slipped to third and fallen more than a thousand votes behind. Gingrich continues to put distance between himself and Perry, too. He now leads by 1,600 votes.

Update: With almost half the precincts reporting, Newt’s lead over Perry has opened up to more than 1,700 votes. Perry’s total number of votes right now is 5,671, so realistically he’s not going to catch Gingrich. What does a fifth-place finish mean for South Carolina? Maybe this:

To participate in the CNN/Southern Republican Leadership Conference debate January 19th, two days before the South Carolina primary, a candidate must place in the top four in Iowa or New Hampshire. A candidate can also qualify for the debate by averaging seven percent support in three polls conducted nationally or in South Carolina by certain approved media and polling organizations.

Either Newt Gingrich or Rick Perry, it appears, will receive the debate invitation that comes with a fourth place finish in Iowa. With 31 percent of precincts reporting, Newt Gingrich is in fourth place (13 percent) and Perry is in fifth place with ten percent support. (Romney, Rick Santorum, and Ron Paul are in a dead heat for first with approximately 23 percent support each).

Perry was right at seven percent in the last Gallup poll of South Carolina. Will he stay there in the next two polls after tonight?

Update: At shortly before 10:30 ET, Fox News says Perry will finish fifth behind Gingrich. No surprise per my last update. He spent $6 million in the state for this; one of the subplots of the coming week will be whether he should drop out and endorse Santorum or Gingrich in order to try to stop Romney.

Update: And right on cue, here’s prominent Iowa social con Bob Vander Plaats (who endorsed Santorum) calling for the rest of the field to consolidate:

Iowa conservative leader Bob Vander Plaats called on Rep. Michele Bachmann to drop out of the Republican race and for Newt Gingrich and Rick Perry to reassess their campaigns following expected lackluster performances in the Iowa Caucuses…

“The worst thing that can happen to Mitt Romney is to run head to head against Rick Santorum,” he said. “He wants to have a multiple candidate field, so I think some of these candidates — they need to reassess where they are at tonight.”

“I think Michele Bachmann has to definitely [drop out],” he added.

Update: A bit of drama towards the end of this boring, depressing horse race: Romney’s come back to take the lead from Santorum by nearly 500 votes with roughly 75 percent of precincts reporting. Paul is now 3,000 votes off the pace and will almost certainly finish third.

Update: See saw: Another batch of votes came in just as I updated. Santorum has surged back ahead with 87.5 percent reporting and now leads by … 45 votes. The spin tomorrow, I assume, will be that Santorum’s made it a race now by showing he can challenge Romney, but I don’t get that. Of course he can challenge Romney in Iowa: It’s tailor-made for him with its heavy evangelical presence and he’s spent months there doing retail politics. Like Ben Smith says, the deeper lesson is that if Santorum can’t even beat a weak frontrunner like Mitt here, where can he beat him?

Update: This’ll get lost in the shuffle tomorrow, but do note that Ron Paul felt confident enough about his position this weekend to predict a first or second place finish. Quote: “I doubt if I’ll come in third or fourth.”

Update: If you can believe it, with 1,629 of 1,774 precincts reporting, the spread between Romney and Santorum is 13 votes.

Update: Bad news for the Not Romney contingent: Bachmann says in her concession speech that she’s going to press on, inexplicably, guaranteeing that the conservative vote splits a bit further in South Carolina.

Update: The first real news of the evening: Perry says in his concession speech that he’s headed back to Texas to “reassess” whether there’s a path to the nomination for him. He was scheduled to go to South Carolina tomorrow to start campaigning, so this is a genuine change of plans. Now that he’s signaled to his donors that he’s wavering, it’s hard to believe he’ll end up pressing ahead. Sounds like it’s over.

Update: Are you ready for the game-changing Maverick endorsement?

Arizona Senator John McCain, his party’s 2008 nominee, will endorse Mitt Romney in New Hampshire tomorrow, a well-placed former McCain aide told BuzzFeed Tuesday.

Update: No foolin’: With 1,749 of 1,774 precincts reporting, Santorum leads with 29,662 votes to Romney’s 29,657. A five-vote margin.

Update: It’s 1:37 ET and we’re waiting on two precincts. I’m taking a screenshot of this for posterity:

The margin is precisely one vote.

Update: As I write this, it’s exactly 2:00 ET and Santorum has a four-vote lead with just one precinct left. But Jan Crawford of CBS has a scoop:

Romney team says he won by 14 votes. Just talked to state party officials.

Philip Klein of the Examiner said earlier on Twitter that this result is less “too close to call” than “too close to care” since the storyline for the next week about Santorum’s surge is already set regardless of who actually wins. True enough. Until we see a New Hampshire poll showing Romney still comfortably ahead, the media buzz for the next few days will be about whether Romney has a glass jaw.

Update: I missed it on Fox but apparently Karl Rove is also hearing that Romney won by 14 votes and that both his camp and Santorum’s camp agree on the numbers. Every last candidate tonight, including Herman Cain and Buddy Roemer, got more votes than the final margin, so every one of them was technically in a position to play kingmaker. If Cain had stuck around and competed in the the caucuses, even with a cloud of suspicion hanging over him due to the harassment charges, he probably would have done well enough to push Santorum back several points, possibly even past Paul.

Update: At 2:34 ET, we finally have an official result. Romney 30,015; Santorum 30,007. Out of more than 122,000 votes cast, just eight separate first and second place. So that’s Iowa; the next big moment will come late tomorrow or Thursday when we get our first post-caucus polls of New Hampshire to see if Santorum, Paul, or even Huntsman are getting some sort of bounce or whether Romney’s got things in hand and we can all start to focus on South Carolina. A report floated by on Twitter a few hours ago that Santorum’s already reached out to Rick Perry. Huntsman, who’s pals with Perry, will no doubt reach out too. He fared badly tonight, but his endorsement would still mean something to social cons in SC or to conservative voters nationwide who might otherwise be leery of giving Huntsman a second look. We’ll see.