For this week’s 2016 Slack chat, the FiveThirtyEight politics teams ponders how important the Iowa caucuses are to Donald Trump.

Check out our live coverage of the Republican debate.

micah (Micah Cohen, politics editor): We’re less than a week out from the Iowa caucuses, and Donald Trump has overtaken Ted Cruz as the most likely winner in the Hawkeye State, according to our polls-only forecast. (And he’s closed the gap on Cruz in our polls-plus forecast.) But there are still doubts about whether Trump can turn out his voters. So, does Trump NEED to win Iowa to win the nomination?

natesilver (Nate Silver, editor in chief): Ted Cruz wins Iowa, John Kasich wins New Hampshire, and Trump emerges as the consensus candidate. I’m joking. Maybe.

harry (Harry Enten, senior political writer): The answer to me is “no, he doesn’t.” I can envision Trump winning without Iowa. But by winning it, he would greatly increase his chances. He’s already over a 50 percent chance to win in both of our New Hampshire forecasts and both of our South Carolina forecasts.

clare.malone (Clare Malone, senior political writer): I don’t think he needs to … he’s the new Teflon candidate, right? Maybe he will even defy the momentum convention. (Look at that rhyme.)

natesilver: OK, I’ll bite. I think an Iowa loss would be pretty bad for Trump. Although maybe not because of “momentum.”

An Iowa loss is bad because the most probable cause of the loss is that his voters aren’t showing up. That means his polls could be inflated everywhere, although probably more in caucus states than in primary states.

The expectations game is harder to gauge, I think, because Trump’s relationship with the media is so oddly codependent.

harry: The question is whether a campaign all about “winning” can take losing. Trump hasn’t lost yet, and the few times he’s gone down in the polls, he’s gone bonkers.

natesilver: He hasn’t lost yet, and he hasn’t really had a moment yet where he had a string of bad polls. It’s interesting too that his top attribute in last night’s ABC News poll was electability. That’s the one where he had the largest lead over his rivals. That contradicts the data showing that Trump is extremely unpopular with general-election voters. But as long as Trump’s winning states and winning in the polls, GOP voters will think he’s a winner, and a great general-election candidate.

clare.malone: I think the idea of how Trump will actually handle losing is an interesting one to contemplate. Being too dismissive or defensive could make the whole enterprise crumble in on itself. People see the Emperor without his clothes, that kind of thing. And for a campaign that seems light on professional political operatives, it would be interesting to see the strategy that would emerge out of an Iowa loss.

harry: Of course, here’s the thing: Even if he loses in Iowa, he still has New Hampshire. Will his 15 to 20 percentage point lead collapse in a week?

micah: It’s possible, right?

clare.malone: I think that scenario is unlikely to happen; maybe Trump supporters in New Hampshire would even be galvanized all the more to get out to the polls and help their guy if he loses in Iowa.

micah: Well, it depends on why he lost in Iowa.

natesilver: If he loses Iowa, it’s also very possible that he’s not actually leading by 15 points in New Hampshire to begin with. You’re underselling the uncertainty in polls. Especially for an unconventional candidate like Trump.

By the same measure, if he way overperforms the polls in Iowa … well, look out, because maybe all those people showing up at rallies really are going to turn out.

clare.malone: What a time to be alive.

harry: Yes, I have to agree with that: two feet of snow in New York and a Trump win in Iowa.

natesilver: Our polls-only forecast has Trump with a 67 percent chance of winning New Hampshire. Which is pretty good for Trump, but also leaves open the distinct possibility he won’t win the state, especially if he loses Iowa.

A 15-point lead — actually, it’s an 18-point lead in our forecast — just isn’t anywhere near as solid in the New Hampshire primary as it would be in a general election. (If a candidate led by 18 points at this point in a general election, he’d be 99+ percent to win.) Especially when there are five other candidates who have some nonzero chance of winning the state.

harry: Right, I should point out that the non-poll factors, such as endorsements, still suggest that Trump isn’t anywhere near as strong as the polls suggest. Now that could mean one of two things.

Endorsements don’t matter — a lack of support from elected officials and party operatives won’t hurt Trump. Or, that the polls may be off. Not in the sense that Trump ends up with 10 percent. But they could be off by enough to throw Iowa to Cruz by a decent margin, and then who knows what might happen.

clare.malone: I don’t think Trump’s supporters care a whit about him having politician endorsements — to me it’s a moot point with them/him. Which defies the traditional patterns we have to go off of.

natesilver: Feel free to throw things at me for saying this, but there’s still a good case that Trump is over-performing the fundamentals. Now, at this point, that may not matter. Even if it’s a bubble, Trump may be able to ride that bubble all the way to the nomination, especially if he wins Iowa. But if something happens to reset the race –— notably, a loss in Iowa — there’s a chance the Trump bubble could burst.

clare.malone: (Harry lobs abacus)

micah: I still think there’s like a 15 percent chance that that happens.

natesilver: And remember, about HALF of New Hampshire voters make up their mind in the final WEEK.

Our elections podcast launched this week. Listen to the full episode above, or subscribe on iTunes.

micah: So, if Trump loses Iowa, how do you all think he responds? Let’s say Cruz finishes with 36 percent and Trump with 25 percent.

clare.malone: I think he tries to spin it as “Iowa doesn’t matter, isn’t like most of the country” and then onward and upward with the arts. He’ll start touting bigtime New Hampshire poll numbers.

natesilver: It’s interesting (and maybe indicative) how y’all have framed that question. In a more traditional race, the big story of Cruz 36, Trump 25 wouldn’t be Trump losing Iowa but Cruz having won it. Cruz is the one who looks pretty Teflon in that case. And he’s Teflon with actual votes, not just in polls.

micah: But that won’t be the story this year.

So if Trump loses Iowa, what does his path to the nomination look like then? I take it he then NEEDS New Hampshire?

harry: If he were to lose Iowa and New Hampshire, it is difficult for me to see how he wins the nomination. It’s not impossible, but I just don’t see it.

clare.malone: I dunno, he could make a lot of inroads in the South. I mean, if he and Cruz are kinda competing for the same voters, this could still be a viable path.

natesilver: Trump could do well in the South, but the GOP’s delegate math doesn’t particularly favor the South. I think you all may be missing the forest for the trees there, though. If Trump loses both Iowa and New Hampshire, that means his big numbers in national polls may have been a mirage all along.

micah: Not necessarily … what if he loses by a hair?

natesilver: He could lose Iowa by a hair without underreporting his polls, but if he loses New Hampshire, that means something pretty significant has changed.

Either some other candidate gained huge momentum, the polls were way inflating Trump’s vote, or both.

Basically everything that I’m saying here boils down to NOBODY HAS VOTED YET. In the primaries, that’s not merely a perfunctory statement. Everything really can change once people start voting.

clare.malone: Nate’s pragmatism really puts a damper on wild-theories-on-a-Tuesday-afternoon time.

harry: Yeah, this point gets lost most of the time; people seem to think that primaries are just like general elections. Primary polling is far less accurate historically, and even if the polls are accurate, primaries can change very quickly. That doesn’t mean they will, but they can.

clare.malone: I mean, basically what we’re all looking to get out of the next couple of weeks is whether or not the Trump house is built out of sand and fog, or if it’s actually viable glass and steel — and then if all these supporters turn out to be real and he wins Iowa, etc., the GOP is really going to have to figure out what the heck to do all the way down the line in this primary season.

natesilver: Let’s spare a few moments for our friend Ted Cruz. Lots of powerful Republicans have spent three weeks trying to knock him out of the running in Iowa. But suppose he survives and wins the state by several percentage points. What does Cruz do then? And what does “the party” do, having fired a blank in their attempt to execute Cruz?

harry: Well, I think Iowa is a very Cruz-friendly state, so I don’t know what it means for “the party” on that score. I do think it’s good news for them, however. I continue not to understand why they are going after Cruz and not Trump. It’s one of the many things this cycle that just makes very little sense to me.

natesilver: Maybe they’re just not that bright. It was the same donor class that threw $100 million behind Jeb!, after all.

clare.malone: Well, Cruz might not play well in a lot of states still — yeah, what Harry just said. He’s playing on a certain kind of conservatism. I think what the party is going to do gets back to a previous chat where we discussed that nothing can be done until the establishment — sorry, Nate, the party elites — decide to unite behind one person. Then they can make better efforts.

micah: [Cue a pro-Rubio argument from Nate.]

harry: Nate loves Rubio like I love snow.

natesilver: Harry stop trying to hide your love for Chris Christie.

harry: Sorry, I’ve moved onto a new beau: John Kasich.

micah: Who does Clare secretly love?

clare.malone: I think I’m the only one without a fave!

natesilver: I thought you wanted to stand with Rand?

clare.malone: No, no. I am a rock. I am an island. No faves allowed.

natesilver: But back to those “party elites.” Weirdly, Trump wins Iowa, that’s a sign that they might have some influence after all.

clare.malone: Wait, why Nate? We can’t assign any of this Trump rise to just the power of the people? The elites always have to be behind it?

natesilver: Trump’s gained 5 percentage points or so in the Iowa polls since party leaders began their anti-Cruz kick.

clare.malone: Or maybe the Trump “he’s a Canadian” thing just worked really well.

micah: I agree with Clare.

natesilver: The timing doesn’t line up with that as well, though.

micah: Canadian + Trump’s general offensive. That timing matches up well enough.

harry: Truth is that it’s difficult to figure out whether X caused Y, or maybe Z did. But I do agree with Nate insofar as it wouldn’t be a negative indicator for party actor support. But again, I think it’s a very dangerous game to hope you can have Trump win Iowa and then beat him later.

natesilver: Yeah, that’s quite a feat they’re hoping to pull off. Kind of insane, really.

micah: So that brings me nicely to a final question: If Trump wins Iowa, how unstoppable does he become?

clare.malone: I think we’re basically all going to say versions of “not unstoppable,” right?

natesilver: Depends on a lot of things, including how Rubio does in Iowa and New Hampshire. If Iowa’s like Trump 31 percent, Cruz 23, Rubio 18 — then Rubio will probably be seen as the main challenger to Trump and might get a boost in New Hampshire.

If it’s Trump 31, Cruz 23, Carson 9, Rubio 8 … well, who knows what, but Trump looks a lot safer then.

micah: Yeah, not to respond to my own question, but I think the answer is: not unstoppable.

natesilver: Yeah, the short answer is “in pretty darn good shape, but not unstoppable.”

micah: Even if he wins Iowa and New Hampshire, a lot can happen. As our own David Wasserman has pointed out: The calendar is friendly to a March establishment comeback.

natesilver: Stop using the E word, Micah.

harry: If Trump wins Iowa, I think he can be stopped. I just don’t know how it happens exactly. I guess, as Nate points out, it would depend on how he did it. For Wasserman’s calendar to work out for the “establishment,” Rubio would probably need to do unexpectedly well in Iowa.

natesilver: There’s always Jim Gilmore, Harry. There’s always Jim Gilmore.

Check out the latest polls and forecasts for the 2016 presidential primaries.