As you watch the debate, keep an eye on which candidates separate themselves from the crowd. That’s because right now, the Republican presidential primary is not so much a race for first place as it is for second and third. FiveThirtyEight’s latest average of national GOP primary polls has Trump at 52 percent of the vote among likely Republican primary voters. DeSantis is a distant second at 15 percent, Ramaswamy is at 10 percent, Pence and Scott are at 4 percent, and Haley and Christie are at 3 percent. Everyone else is below 1 percent.

Trump’s lead will be very hard for the other candidates to close — so their best hope at this point is to stay in the game, in case Trump drops out (unlikely as that seems right now) or something else changes. DeSantis is currently in position to be the would-be front-runner if Trump drops out, but depending on debate performances and other factors, he could wind up in a close race with one of the other candidates currently clustered in that 5-10 percent range.

-Analysis by G. Elliott Morris of FiveThirtyEight

Chris LaCivita, a senior campaign adviser to Trump, said on the conservative “Ruthless” podcast streamed live before the debate that Trump does not currently plan to attend the second GOP debate, set for next month in California, but indicated that Trump could change his mind.

"He's not going to be in California ... Well, first of all, with President Trump, you know, he could change his mind at any moment … And you should just assume that he won't until he does,” LaCivita said.

Both fellow primary candidates and GOP officials have urged Trump to be on the debate stage, although some candidates have downplayed the significance of his absence.

-ABC News’ Laura Gersony

Hours before eight Republicans take the debate stage, Democrats appear to be going on offense around the site of the event.

The Biden campaign rolled around a mobile billboard around Milwaukee’s Fiserv Forum which depicts “Dark Brandon” -- President Joe Biden’s satirical alter ego.

The billboard hits Republicans on their abortion positions, particularly their support for restricting the procedure.

-ABC News' Fritz Farrow

Trump campaign surrogates like Rep. Marjorie Taylor Greene, R-Ga., have been spending the day on media row touting Trump’s policies to various news outlets. She has plans to host a post-debate analysis show with Rep. Matt Gaetz, R-Fla., on conservative outlet Right Side Broadcasting Network.

Donald Trump Jr. and Kimberly Guilfoyle have also been live-streaming for his podcast outside the debate arena since Wednesday afternoon, joined by other Trump surrogates like Greene, Gaetz, and Kari Lake.

On the podcast, Donald Trump Jr., Guilfoyle and various surrogates sought to downplay the debate, calling the stage a “VP debate,” a “kids’ table” at a Thanksgiving dinner, and a “secretary of education debate.”

Other candidates have criticized the former president for declining to face them and make his pitch to voters in Milwaukee.

Lake on the Donald Trump Jr. podcast also said she spoke with the former president earlier on Wednesday afternoon about the pre-taped Tucker Carlson interview scheduled to be released Wednesday, saying it will be a “good interview.” She said the elder Trump sounded “really good” in the afternoon but told her that “things are going to get worse before they get better.”

-ABC News' Soo Rin Kim and Lalee Ibssa

Trump maintains a lead of 28 percentage points over his nearest competitor in South Carolina, according to the latest polls.

Haley and Scott, the two candidates from South Carolina, are both polling higher in South Carolina than they are nationally, according to our polling average. Trump is polling about 7 points lower in South Carolina than in national polls.

Only one pollster, the Manhattan Institute has tested the favorability of Republican candidates in South Carolina since July 1. That survey found Scott and DeSantis had the highest net favorability in the state (+56 and +55 percentage points, respectively), and Trump and Haley close behind (+39 and +33 points, respectively). Pence had a net favorability of +1 point, and Christie was underwater by -36 points.

Economic issues are most important to Republican primary voters in South Carolina, according to a July survey from Fox Business/Beacon Research/Shaw & Co. Research. Fifty-one percent of Republican voters said economic issues would be most important for deciding their vote. Twelve percent each said immigration issues, social issues and foreign policy were most important.

In an August survey by National Public Affairs, 40 percent of South Carolina Republican voters said that Trump wouldn’t lose their support even if he did not show up to the debate. Twelve percent said that they support Trump, but if he didn’t debate they would be open to or definitely supporting someone else, 32 percent said they wouldn’t vote for Trump regardless, 9 percent said they probably wouldn’t watch the debate anyway and 6 percent were unsure.

-Analysis by FiveThirtyEight