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

As Republican candidates gear up for the debate, many have specific rituals they’ll be doing in preparation.

A campaign adviser for Haley said she will be listening to music, “lots and lots of music: Joan Jett, Queen, Def Leppard and [the] Go-Gos, to name a few.”

DeSantis has spent today with his wife, Casey, and their three children, though a campaign spokesman offered few details about how the family has spent their time.

Hutchinson posted a photo of himself preparing with notepad and laptop in hand.

“Some last minute studying and prep for tomorrow! It’s important to show up and be ready to answer the tough questions, you deserve nothing less than a leader ready to lead on day one,” Hutchinson captioned the photo online.

Pence will plan to spend time in prayer before the debate, while Scott took a tour of the debate stage, which he posted a video of, along with encouragements from his family, to X, formerly known as Twitter.

Others prepared physically, earlier this week.

Ramaswamy posted videos to X of himself playing tennis and him and his wife doing floor exercises in a gym throughout the lead-up week.

Burgum was playing a stress-relieving pickup game of basketball on the eve of the debate, according to a campaign press secretary, when he sustained an Achilles injury that called into question his ability to participate in the event.

He will be participating, albeit on crutches, per a photo posted to his X account.

-ABC News’ Gabriella Abdul-Hakim, Libby Cathey, Abby Cruz, Will McDuffie and Olivia Osteen

Recent initial primary debates have involved a lot of candidates — 17 for Republicans in 2016 and 20 for Democrats in 2020 — across two debates, either on the same night or across two evenings. To lead off the 2024 cycle, Republicans will have a more intimate affair, with eight contenders taking the stage tonight. That number could’ve been slightly larger, however, as nine GOP candidates met the RNC’s debate qualification criteria for polls and donors. But Trump isn’t participating, having refused to sign a mandated loyalty pledge promising to support the eventual GOP nominee in the general election, so there will be only eight lecterns on stage.

Eligible participants either earned 1 percent support in three national polls or at least 1 percent in two national polls and two polls from the first four states voting in the GOP primary (each coming from separate states), based on surveys that meet certain criteria for inclusion. They also attracted donations from at least 40,000 unique contributors, with at least 200 donors from 20 or more states and/or territories.

Meeting these criteria was straightforward for most of the candidates, as by the end of July, seven (including Trump) had enough qualifying polls and donors to make the stage. Lagging behind, Pence became the eighth eligible contender when his campaign announced on Aug. 7 that he brought in enough unique donors. Hutchinson had enough surveys in hand by late July, but he only announced on Sunday that he had reached the 40,000 donor mark, coming in just under the deadline.

But there was last-minute drama, as businessman Perry Johnson and Miami Mayor Francis Suarez each said they had qualified, only for the RNC to leave them off its final list of participants. Johnson in particular may have a bone to pick, as he claimed that the RNC initially indicated that he had enough polls, and our analysis suggests he did, too. Larry Elder, who along with Johnson hasn’t met FiveThirtyEight’s criteria for being considered a major candidate, also claimed he had made it,> but one of the polls he cited did not have a large enough sample size to meet the RNC’s criteria. Johnson and Elder announced yesterday that they were suing the RNC. Suarez, Johnson, Elder and Hurd all had enough donors to make the stage but, controversially or not, lacked the polls in the end.

-Analysis by Geoffrey Skelley of FiveThirtyEight

The 2024 presidential election has been underway for months, but with tonight’s first Republican primary debate in Milwaukee, we’re kicking off a new phase of the campaign. In these final five months before voting begins, we’re going to have monthly debates, dashes through Iowa, big-money fundraisers — and probably a culling of the field.

Tonight’s debate will feature eight candidates. Front-runner Donald Trump, who has a 37-percentage-point lead in FiveThirtyEight’s national polling average, will not be among them, as he has opted to skip the debate. Instead, we will hear from Florida Gov. Ron DeSantis; entrepreneur Vivek Ramaswamy; former Vice President Mike Pence; Sen. Tim Scott; former U.N. Ambassador Nikki Haley; former Arkansas Gov. Asa Hutchinson; North Dakota Gov. Doug Burgum; and former New Jersey Gov. Chris Christie.

There are a few threads and tensions we’re going to be watching tonight. First, in the absence of Trump, will his challengers’ attempts to position themselves as a more favorable option fall flat? How will candidates make their case for being a better alternative to Trump without having the contrast on stage beside them? Secondly, what sort of friction will we see between the anti-Trump candidates and those running on more similar ideas or rhetoric?

We’ll keep an eye on all this and more. You’ll be hearing from the crew at FiveThirtyEight and ABC News — as well as some new friends at PolitiFact — throughout the night. The Fox News-hosted debate begins at 9 p.m. Eastern, and we have some colleagues on the ground in Milwaukee who will ensure you’re going in with everything you need to know.

Thanks for joining us. Stay tuned as we update the blog with real-time analysis, charts, thoughts, questions, ideas, idle fancies and more. Leading up until the debate starts, we’ll run through the state of the race so far. Once the debate starts, we’ll make sure we’re addressing everything happening on stage, including what issues the candidates talk about, who they attack, how they position themselves and what Americans think.

-Analysis by Maya Sweedler of FiveThirtyEight