What We’re Watching For In The Second Democratic Debate

Welcome to FiveThirtyEight’s weekly politics chat. The transcript below has been lightly edited.

sarahf (Sarah Frostenson, politics editor): It’s hard to believe it’s been a month, but the Democratic primary debates are baaack. And on Tuesday and Wednesday evening, 20 candidates (10 each night) will take the stage, with one potentially big new showdown (Elizabeth Warren vs. Bernie Sanders) on the first night and one big rematch (Kamala Harris vs. Joe Biden) on the second night.

For reference, here’s Tuesday’s lineup: Bernie Sanders, Elizabeth Warren, Pete Buttigieg, Beto O’Rourke, Amy Klobuchar, Marianne Williamson, John Delaney, John Hickenlooper, Tim Ryan, Steve Bullock.

And Wednesday’s: Joe Biden, Kamala Harris, Cory Booker, Andrew Yang, Julián Castro, Tulsi Gabbard, Michael Bennet, Jay Inslee, Kirsten Gillibrand, Bill de Blasio.

So yes, let’s talk about the lineups and matchups, but first let’s also take a step back to talk about the role of primary debates — how do they change the race?

nrakich (Nathaniel Rakich, elections analyst): I think it’s clear that debates can change the race. But the effects might be fleeting, as after one debate the race might move in one direction while subsequent debates might push things in a different direction.

natesilver (Nate Silver, editor in chief): Debates also tend to ramp up in importance as the campaign goes along. It might feel like we’ve been covering this race forever. But we’re still in the rather early stages, as far as voters are concerned.

julia_azari (Julia Azari, political science professor at Marquette University and FiveThirtyEight contributor): I think I might have a slightly different take on this than Nate. My sense, based on the research, is that the debates will produce diminishing returns as opinions become solidified, but that might apply more for minor candidates than for contention between major ones like Harris and Biden. (Though there’s still a notable big name-recognition gap between the two.)

nrakich: I’m with Julia on this one. In 2016, the first Democratic primary debate had the highest ratings.

natesilver: But in some sense, the purpose of these early, very-inclusive debates is to see if any of the minor candidates can break through. Which didn’t really happen after the Miami debates, although you could argue the case for Castro I guess.

sarahf: Castro was interesting. His favorability numbers shot up, but he didn’t really see as much of a swing in support, or at least that is what we found in our poll with Morning Consult.

nrakich: But Castro is a great example of someone for whom the debates could build on each other to increase his support. He got people’s attention in the first debate; maybe, with another good moment this week, he’ll start to get their support. Or at least get enough backing to clear the third-debate thresholds.

natesilver: I’m skeptical that Castro is likely to break through. I mean, shouldn’t we take the opposite lesson from the first debates, in fact? That you can have a good debate and it doesn’t help you break through because the top of the field is pretty entrenched?

nrakich: We didn’t say he was likely to, though — just that the possibility existed.

He’s already at 130,000 donors, the threshold for the third debate, in large part due to his first debate performance.

natesilver: I guess I’m just saying that I think people are maybe underestimating how much voters like the top-tier candidates when they say they expect a middle-tier candidate to break out.

julia_azari: What we’ve seen so far leaves me questioning whether the top tier is really open to newcomers at this point. I think there’s contention over who will be in that second tier of candidates who meet the requirements for the fall debates, but most of those candidates won’t come close to winning the nomination.

sarahf: Or maybe even making the next debate!

This might be the last time we see many of these candidates on stage because September’s qualifying thresholds will be difficult for them to meet. (Candidates must have at least 2 percent support in four recent qualifying polls1 and 130,000 unique donors.2)

natesilver: There are a lot of middle-tier candidates, so what are the odds that at least one of them will break into the top tier at some point in the race? Maybe fairly high. Let’s say it’s 60 percent, just to make a number up. But that 60 percent is divided between a lot of different candidates.

sarahf: OK, so as to this top-tier vs. middle-tier debate …

Let’s look at night one and unpack some of the dynamics there. As a reminder, night one includes: Sanders, Warren, Buttigieg, O’Rourke, Klobuchar, Williamson, Delaney, Hickenlooper, Ryan, Bullock.

So given the lineup, there’s potential that some of the more moderate candidates — say, Buttigieg, O’Rourke and Klobuchar — maybe try to position themselves against Warren or Sanders, right? And that can maybe help them break through to the top tier? Or at least make the top tier look less fixed?

julia_azari: Yeah, “Can a middle-tier candidate move up?” seems like the unofficial slogan of night one.

sarahf: More so than night two?

julia_azari: I think so. But I reserve the right to flip-flop if one of you convinces me.

nrakich: Agreed, and in fact I’d pay even closer attention to the lower-tier candidates: Hickenlooper, Ryan, Bullock, Delaney. They know that this is their last chance to make a splash before the third debate’s stricter thresholds. And they all have little love for Sanders’s socialism/Warren’s progressivism.

I think they will lash out pretty hard.

julia_azari: And, in fact, I might convince myself to flip-flop because of the timing. If Buttigieg, O’Rourke or Klobuchar has a strong performance (say, on the level of Castro last time) and emerges as the official Biden Alternative for the Heartland Moderate (or whatever, don’t @ me), I think there’s still a strong chance that something else happens on night two that overshadows it.

nrakich: I also think the potential for Sanders-Warren fireworks is overrated. Despite their ideological similarities, they aren’t really competing for the same bloc of voters. Warren supporters are more likely to be higher-income or have a college degree, while Sanders’s support is more working-class.

natesilver: I strongly disagree with Rakich on the Sanders-Warren lanes thing!

sarahf: