Labor Day, when campaigns traditionally begin to rev up, is in the rearview mirror, and the Republican primary field is still crowded and messy. But Ben Carson, a neurosurgeon, has been climbing in the polls. FiveThirtyEight’s politics team gathered in Slack to talk about the Carson “surge.” This is an edited transcript of the conversation.

micah (Micah Cohen, senior editor): Nate and Harry, Ben Carson is on the upswing in national polls. Check out the light teal line here:

He’s also made gains in Iowa:

And he’s done so largely without the media’s help. Will the Carson surge just be a blip à la Michele Bachmann and Herman Cain in the 2012 cycle? Or can Carson take down The Donald?

natesilver (Nate Silver, editor in chief): I, for one, look forward to the Carson-Trump unity ticket and a close general election against Biden-Warren.

hjenten-heynawl (Harry Enten, senior political writer): Well, let’s start off with a look at the latest polling. We see Carson climbing, but we see him doing much better in Iowa than in New Hampshire. This weekend, for instance, a new Marist poll had Carson in second place in Iowa, with 22 percent, and in third place in New Hampshire, with 11 percent. And take a look at which groups Carson is doing best with in Iowa: It’s white evangelicals. That’s unlike Trump, who tends not to outperform with any one group in particular.

natesilver: Indeed, it doesn’t seem like Carson’s and Trump’s supporters have all that much in common. Which is good news for Trump, in a way? Still, part of the question is what would happen if Carson started to command some of the media attention that Trump was monopolizing previously.

micah: I feel like Carson is starting to get some attention.

hjenten-heynawl: Trumpnado may be degraded from different angles. You knock him in Iowa with Carson, then you hit him in New Hampshire with John Kasich (or Jeb Bush).

But on the media coverage, you could easily see Trump come back to the pack merely as a result of Carson gaining attention in Iowa, which could open the door to non-Trump candidates elsewhere.

natesilver: Well, there’s a discussion about whether Iowa is a “must-win” for Trump. To the extent that his support in polls partly reflects a bandwagon effect — people think he’s a winner because he’s leading in the polls and that all the other GOP candidates are losers — finishing second or third in Iowa could hurt him.

But we’re probably also getting way, way ahead of ourselves. If Trump’s relying on a bandwagon effect, then what happens if Carson passes him in some national polls, for instance?

hjenten-heynawl: Let me point out one other big difference between Carson and Trump. Carson’s favorable rating in the latest Monmouth University poll was 67 percent. His unfavorable rating was just 6 percent. Trump, even with improving favorables, was at a 59-29 split.

micah: So aside from stealing some of the spotlight from Trump, can Carson eat into his actual support? They’re certainly different stylistically (Trump is loud, Carson is quiet), and as you said, Trump draws about equally from across the GOP, while Carson pulls support from the evangelical right. But neither has held office before; they’re both outsiders. Can Carson steal some actual Trump backers?

natesilver: Can I make an observation? It’s interesting that we’re succumbing to the temptation of filtering all questions about the GOP primary through the lens of Trump.

micah:

natesilver: I think Carson and Trump are actually pretty different. Not just in their presentation. Their policy positions are pretty different. Carson has more or less conventional conservative / tea party positions. Trump, uh, doesn’t.

hjenten-heynawl: Right. I would say that Trump really isn’t much of anything. He’s more an attitude than an ideology. Carson, on the other hand, has specific groups with whom he does best. This, I think, is a key difference. To me, Carson is much more like something we’ve seen before. Trump, on the other hand, is more of an original.

natesilver: I’d also argue, though, that Carson is a little bit different from the “flavor-of-the-month” candidates from 2011. At least in terms of his demeanor, he’s much less bombastic than someone like Gingrich or Bachmann. And he has a much more compelling life story — it’s not an exaggeration to say it’s a heroic life story.

micah: Carson may not yell, but he has said some pretty Trumpian things.

hjenten-heynawl: This is why I think Carson is dangerous to someone like Trump. Even when he says something that certain people might call politically incorrect, he says it with a smile.

And this makes him far more likable, while still “telling it like it is.”

natesilver: I don’t know @micah. He’s said a few Trumpian things. But Bush and Scott Walker have had a few of their own gaffes too, for example.

If you watch Carson’s announcement speech, he’s pretty mild-mannered and low-key throughout:

At the very least, he’s a little hard to characterize. Which is part of the reason he hasn’t gotten that much press coverage, methinks. He doesn’t fit that neatly into any of the media’s templates for a candidate.

micah: So that suggests he could have more staying power than a Bachmann or Cain?

hjenten-heynawl: I’ve learned that it’s difficult to predict how long a surge will last. But what we can say is that Carson isn’t going up against a mainstream Republican. He’s going up against Trump. Carson is also much better-liked across the party than either of the two you noted. So the recipe is there for a little more staying power.

natesilver: So, Harry. Who is more likely to be the Republican nominee, Ben Carson or Donald Trump?

micah: Good question! No hedging, Harry

hjenten-heynawl: Ben Carson, and I’m not sure there is much doubt in my mind. Reasons include:

He’s better-liked by Republican voters, at least at this point. He’s better-liked by party actors. He has a much more presidential demeanor than Trump. He also happens to be African-American at a time the GOP wants to reach out to black voters.

This isn’t to say he is anything more than a long shot, but he’s a trip to the West Coast while Trump is a trip to the moon.

micah: And, Nate, how would you answer your own question?

natesilver: Hold on — I’ve gotta take a phone call here …

micah: We’ll wait …

natesilver: [crickets]

micah: Coward.

natesilver: I guess I’d put each of their chances at about 5 percent.

micah: Interesting. You don’t buy Harry’s argument? Or his West Coast/moon metaphor?

natesilver: Obviously, Carson has much higher favorables. He also has policy positions that are much more in line with the GOP mainstream. So, you can imagine a universe in which GOP elites grudgingly tolerate Carson, even if he’s not their first (or second or third or sixth) choice, whereas they’ll do everything in their power to make sure that Trump is not the nominee.

On the other hand, Trump has survived quite a bit more scrutiny so far. Not very much scrutiny as compared to what he’ll face between now and February. But some of it, certainly, and much more than Carson.

Furthermore, it’s not clear to me how interested Carson is in actually becoming president. Or how much relevant experience he has in running a campaign. Trump’s experience as a celebrity and mogul and television star is more transferable to the political stage than Carson’s as a neurosurgeon.

Put another way, when Carson says he’s not a politician … that might be somewhat literally true. Whereas it’s a rhetorical line for Trump.

hjenten-heynawl: I would give Trump a better chance of getting say 10 or 15 percent in the primary vote, but I’d give Carson a better chance of winning the nomination. Even if everything goes right for The Donald, a wall likely awaits him (and not the wall he wants). Carson, on the other hand, may flame out. But if he can keep his stuff together, then you could potentially see him coming close to the nomination. Again, neither has all that great of a shot.

natesilver: We’ve talked before about whether Trump fits into the template of a bandwagon candidate (like Newt Gingrich or Cain) or a factional candidate (like Pat Buchanan). The answer could be: both?

So sooner or later — maybe later! — his numbers fall to Earth a bit. But he’s still left with 15 percent support, or something.

Trump has led the polls for two months or so. But he’s led them in July and August, at which point there’s not very much real political news. And there was only one debate, as compared with the more active schedules in past years.

So in political time, those two months aren’t really very long. This is probably a slight exaggeration, but it might be easier to lead the polls for two months in July and August than for two weeks in December, for instance. We still have a lot to learn about how GOP voters will behave as the campaign evolves.

micah: If the Trumpnado is deprived of oxygen, where do his voters go?

hjenten-heynawl: I think Trump supporters could go any and everywhere. They tend to be more anti-Washington than voters on average, but they aren’t any more liberal or conservative. That’s why Bush and Walker and Rand Paul (among others) have all fallen even though there isn’t an ideological tie between them. I think Carson can eat away at Trump’s Christian Conservative voters, but overall, there isn’t a natural home for Trumpers.

micah: Last question — we’ve talked before about whether the GOP establishment was losing control of the nominating process and decided they weren’t. Have Carson’s gains (or Carly Fiorina’s) made either of you rethink that? The more establishment candidates — Jeb Bush, Scott Walker, Marco Rubio, John Kasich (outside of New Hampshire) — still have yet to gain much traction. Is something different this time? (BROKERED CONVENTION!!!!!!!)

hjenten-heynawl: Talk to me when we aren’t five months out from Iowa, or if there is one candidate who receives the lion’s share of endorsements and doesn’t win any states. Or put another way, I’ll start rethinking that when a candidate who isn’t well-liked by the party actors wins a bunch of states.

natesilver: OK, but a couple of things are different this time around. First, there are 17 candidates running.

hjenten-heynawl: Jim Gilmore is not a real candidate. Just FYI.

natesilver: Fine, 16 candidates. Secondly, as you pointed out the other day, Harry, the GOP establishment has never been quite so slow to settle on a candidate, at least judging by the number of endorsements.

hjenten-heynawl: Things may be different for Republicans, but we have examples of this on the Democratic side. You can look at 1988 or 2004 on the Democratic side, but from each field, you got what most would call a traditional candidate.

natesilver: Examples where there were 17 candidates running? (Err, 16?) Maybe 1972 on the Democratic side. But that resulted in George McGovern, who certainly wasn’t an establishment favorite, winning the nomination.

hjenten-heynawl: I’m talking about very large fields. Look at 1988 on the Democratic side (from Wikipedia):

natesilver: Harry, you’re including some very dubious “candidates” on that 1988 list.

hjenten-heynawl: Take it up with Wikipedia. I mean, there are some “dubious” candidates on the GOP side, like George Pataki. Either way, yes, 17 or 16 is a lot, but we’ve had 10+ candidate fields before — fields that winnowed and worked their way out. I’m more than open to saying this time could be different, but we should also say that it’s still early and we should let the priors lead the way.

natesilver: Sure, I agree that the most likely outcome is some establishment-ish candidate — Bush, Rubio, Kasich, Walker — gaining momentum at the right time and winning the nomination. It’s still very early — too early to be paying much attention to polls. And if you do want to look at polls, Rubio and Walker have very high favorability ratings, which speaks against the notion that GOP voters are rejecting establishment choices wholesale.

But I also don’t think we should be all “LOL, brokered convention.” It’s not that far-fetched this year, as compared to most years in the past.

hjenten-heynawl: What’s far-fetched?

natesilver: In our chat a few weeks ago, I put the chance of a nomination that was genuinely uncertain in June (after the last primaries and caucuses) at 20 percent. (That’s not quite the same thing as a brokered convention, since the nomination could be resolved through backchannels before the convention convened.)

Maybe I’d put the chance at 25 percent now? Nothing all that fundamental has changed. But if there’s a universe where Trump is winning some delegates and someone like Carson or Ted Cruz is winning some also, that makes the GOP’s math a little messier.

hjenten-heynawl: Wow, that’s quite high. I’d put it closer to 10 percent. Granted that’s higher than I give the chance of Carson winning the GOP nomination.

micah: We’ll have to agree to disagree, and the readers can decide who’s right in the comments. Thanks, everyone!

Check out our live coverage of the second Republican debate.