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

Nikki Haley has been in the race for longer than anyone else on the stage but hasn't had a breakout moment yet. She was clearly aiming to change that tonight, and she did have one of the most memorable back-and-forths of the night when she took Ramaswamy to task over his lack of foreign policy experience. She came out swinging early not just against Biden but against Republicans in Congress, and she was one of just a handful of contenders to make an electability argument against Trump by pointing out his low favorability ratings. But for a candidate who is polling at 3.4 percent nationwide, it's not obvious that was enough.

Burgum's presence was a victory in and of itself for the governor, given his injury today. But he got scant talking time, and his most interesting answer, when he came out definitively against a national abortion ban, isn't likely to earn him many new fans in the GOP.

But here's what I really think. The next debate is not for another month, but tomorrow, Donald Trump will surrender to the authorities in Atlanta. His mugshot will ricochet across the internet and land on the front page of every major newspaper in the country. At that point, will people be talking about tonight's debate? Or will they be back to talking about Trump? I'd put my money on the latter, and that's not good news for anyone on stage tonight.
-Analysis by Jacob Rubashkin, Inside Elections