The Republican presidential candidate with the most institutional support is the one who decided not to show up tonight: Trump. He has 364 endorsement points, according to 538’s endorsement tracker, which assigns a certain number of points to each endorsement a candidate gets depending on how prominent the endorser is. DeSantis is in second place, but way, way behind, with 43 endorsement points.

This is important because the candidate with the most endorsement points by the time of the Iowa caucuses usually wins the nomination. Given how strong Trump’s polling lead is at the moment, one of the few things that could (maybe) stop him is Republican party leaders closing ranks around another candidate. So far, there’s no sign of that happening.

—Analysis by Nathaniel Rakich of 538

In anticipation of tonight’s debate, we again partnered with The Washington Post and Ipsos to ask likely Republican primary voters what they think about tonight’s debate participants and the candidate field in general.

The 5,002 likely Republican primary voters we polled using Ipsos’s KnowledgePanel expect DeSantis and Ramaswamy to perform best, out of the seven-candidate field. According to a five-point scale that we calculated using respondents’ answers (with 1 being “terrible” and 5 being “excellent”), likely voters expected both DeSantis and Ramaswamy to perform “very good” (3.44 and 3.43 out of 5, respectively). They thought Haley would perform third-best (3.40 out of 5) and Scott fourth (3.20 out of 5). All of this is fairly in line with their pre-debate expectations in August.

When it comes to which candidates respondents are interested in, Haley saw the biggest bump since our poll before last month’s debate — 31 percent are now considering voting for Haley, up from 25 percent. Although she now has the third-most prospective support, she’s still got a long way to go compared to Trump (66 percent) and DeSantis (49 percent). About 1 in 4 likely Republican primary voters are also considering voting for Ramaswamy and Pence.

We’ll be watching to see how the candidates fare tonight, and if debate watchers’ opinions on who they’re considering voting for will change after tonight’s performances.

—Analysis by Holly Fuong of 538

Outside of the Trump-critical wing of the Republican primary — featuring Christie and Hutchinson, with major appearances by Pence — most of the presidential field has tip-toed around Trump, careful not to attract his ire. But in the last couple weeks, some candidates have started taking on Trump more directly, jeopardizing their prospects as his running mate.

Trump was already unlikely to name a challenger as his VP pick. Of the 19 unique Democratic and Republican presidential nominees since 1972, only four selected a running mate who had run against them in the same year’s primary. And Trump is even more prickly about loyalty than his recent predecessors.

Last week, we analyzed the tweets of the six highest-polling Republican candidates (other than Trump) in 538’s national polling average. Until recently, DeSantis had hardly acknowledged the former president, mentioning Trump just once since Jan. 6, 2021. But that changed last week, when DeSantis published three critical tweets about Trump. Scott, meanwhile, has largely kept his social media tone neutral toward Trump, but we did see a rare direct criticism on the stump last week, when he said Trump’s suggestion that he’d seek a compromise on federal abortion legislation was the wrong approach. Haley’s tone toward Trump shifted earlier this summer, from cautious to directly critical.

Tonight could tell us whether these recent instances of criticism are the beginnings of a new trend in which the GOP field actually tries to topple the front-runner.

—Analysis by Leah Askarinam of 538

Everyone obsesses over horse-race polls, but another important data point in the primary is each candidate’s net favorability rating, or the share of Republicans who view them favorably minus the share who view them unfavorably. In a horse-race poll, respondents can only choose one option, but in reality, there are probably multiple candidates they might consider voting for. Net favorability rating gives us a proxy for how many voters might be open to supporting a given candidate, even if they are not currently a voter’s first choice.

Unsurprisingly, Trump is the most popular candidate in the GOP field, with a net favorability rating of +53 percentage points among Republicans, according to the 538 average. But DeSantis isn’t too far behind him at +43 points, indicating that, although he isn’t many Republicans’ first choice, most of them still like the guy. Ramaswamy, Scott and Haley also have strongly positive net favorability ratings, suggesting that they are the five most plausible Republican nominees. By contrast, Pence and Christie are underwater with Republican voters, making it difficult to see how they can win the nomination.

—Analysis by Nathaniel Rakich of 538

I'm at the Reagan Library in Simi Valley, California, for the Republican debate tonight and so far it's been a Democrat who's caused the biggest stir in the spin room. California Gov. Gavin Newsom came through for an interview with Univision and a rather lengthy gaggle with the national press corps. He defended his decision to debate DeSantis later this year, defended his presence at a Republican debate in the first place and he answered a question from yours truly.

I asked him about one of the issues that Biden is currently faring worst with the American public on: immigration, and specifically border security. Newsom told me he supports Biden's plan on this issue, but that: “The one thing I would add to it, not what’s wrong with it, is we need to do more on the asylum space as it relates to how the asylum system is being gamed and that is legitimate.”