The Biden-Harris campaign appeared to buy airtime on Fox News ahead of the GOP primary debate, with ad advertisement for the Democrats’ reelection campaign running just minutes before the eight Republican hopefuls took the stage.

The ad, which acted as something of counter-programing to what the GOP hopefuls may discuss during the two-hour debate, touted what the Biden administration sees as its legislative accomplishments, like the American Rescue Plan, the Inflation Reduction Act, the CHIPS and Science Act and the Bipartisan Infrastructure Law.

The spot highlighted the economy under Biden, which is likely contrary to what the Republican primary candidates will raise on stage -- citing Biden's low marks from voters on his handling of economic issues.

–ABC News’ Isabella Murray

I’m monitoring Christie and Scott tonight. Even though the two candidates are polling similarly in the 3 to 4 percent range in FiveThirtyEight’s national polling average, they are a subject in contrasts. Although Pence has been more vocally critical of Trump recently, Christie is the most high-profile, full-on anti-Trump candidate on stage. Realistically, Christie has very little chance at the GOP nomination because he has negative net favorability ratings among Republicans. But that may mean he will focus almost entirely tonight on attacking Trump rather than making appeals to the party base. As a result, Christie could be a popular foil for the contenders on stage who have largely eschewed going after Trump, or have even defended him.

Meanwhile, Scott arguably has one of the highest ceilings of any candidate on stage. He’s not nearly as well-known to GOP voters as Trump or DeSantis, but Scott gets rave reviews from Republicans who are familiar with him. That means tonight is an opportunity for him to expand his reach and also potentially increase the share of GOP primary voters who would consider voting for him. I’ll be interested to see how much he leans into his “happy warrior” image as a means of differentiating himself from DeSantis and Ramaswamy, and whether he tries to rise above the fray to some extent if some of the other candidates — especially Christie — get into verbal fisticuffs.

–Analysis from Geoffrey Skelley

I’ll be watching Ramaswamy tonight, who will be center stage next to DeSantis, a position I did not foresee for the biotech entrepreneur when he first jumped into the race in February. But Ramswamy is on an upswing, soaring from a virtual unknown to garnering nearly 10 percent in FiveThirtyEight’s national polling average. Without Trump on the stage and with DeSantis’s polling average trending downward, is it Ramaswamy’s moment to own it?

Ramaswamy has staked his candidacy on an anti-woke, pro-capitalist message, promising to guide the country at a revolutionary moment by recognizing 10 simple truths. He’s a 38-year-old millennial leaning into the culture wars from the right who often seems to say exactly what pops into his head. This style has so far made him a major candidate. We’ll see tonight whether it appeals to voters. Thirty percent of likely Republican primary voters view him favorably, according to a FiveThirtyEight/Washington Post/Ipsos poll released today, and only 10 percent view him unfavorably. That leaves a huge chunk of voters in the middle who say they don’t know much about him and who may be seeing him speak at length for the first time during the debate. How he performs — whether it involves quoting Eminem or not — could leave a lasting impression. And a newcomer without political experience coming out of nowhere to win the Republican nomination? It’s something we’ve seen before.

–Analysis from Monica Potts

I’m tracking Burgum and Haley tonight. In another universe, the two might be top-tier contenders — a billionaire two-term governor from the heartland with great hair, and a trailblazing former governor and U.N. Ambassador long seen as a rising star in the GOP — but neither have made much of an impact on the race so far. Haley had a brief moment of prominence in February, when she was the first non-Trump candidate to jump in the race, but has since polled consistently in the low single digits. Haley will be the only woman on stage, and she may try to play to her strengths by drawing sharp foreign policy contrasts with higher-polling contenders like DeSantis and Ramaswamy (who she went after over Israel policy this week). Most of the attention Burgum has received surrounds his innovative tactic of paying people to donate to his campaign. The North Dakotan has been polling marginally better in Iowa and New Hampshire, where he’s spent millions on TV ads. If he makes it to this debate — he was in the emergency room earlier due to a basketball-related injury — his task will be to tell voters who he is, since he’s one of the least-known people on the stage, and maybe sell his Trump-free economic argument.

–Analysis from Jacob Rubashkin, Inside Elections

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