Governors Newsom and DeSantis head to the debate stage Thursday as the two jostle for influence in their respective parties in the shadow of their aging but dominant leaders.

The event, mediated by a Fox News host, Sean Hannity, and billed as “DeSantis vs. Newsom: The Great Red vs. Blue State Debate,” is ostensibly going to be focused on the merits of the two governors’ records at the state level, but is sure to see each governor’s ambitions bleed through.

Messrs. Newsom and DeSantis have been sparring for years over topics ranging from Covid-era policies to the handling of migrants in their states.

A spokesman for Mr. DeSantis’s campaign, Andrew Romeo, tells the Sun that the debate “will be the first chance for Republicans to contrast our vision for the future of the country with the failed agenda of someone who very well could become the Democrats’ nominee.”

“A Newsom presidency would accelerate America’s decline, and Thursday will be the first chance to expose to a national audience just how dangerous his radical ideology would be for the country. Ron DeSantis will take this responsibility seriously,” Mr. Romeo says. “He looks forward to sharing the stark contrast between his vision to revive our nation and Newsom’s blueprint for failure.”

Mr. Newsom’s office did not immediately respond to a request for comment from the Sun.

The goal of the debate, according to a statement Fox News made to the Hill, is to “examine the vastly different approaches the two governors have and offer insights into their political philosophies as well as ambitions for the nation.”

The network added that the debate would cover topics “including the economy, the border, immigration, crime, and inflation.”

The debate was agreed to in September after sparring between the governors came to a head when Mr. DeSantis’s Florida Division of Emergency Management surprised officials at Sacramento with a planeload of migrants.

Mr. Newsom characterized the move by Mr. DeSantis as a political stunt and in a statement called the Florida governor a “small, pathetic man,” later telling NBC News that Mr. DeSantis was “flailing” and “desperate for attention.”

Both governors have also been working to raise their national profiles.

Nationally, Mr. DeSantis is working to retain his title as the most popular non-Trump Republican in the GOP’s presidential primary. Yet Ambassador Nikki Haley has been nipping at his heels in national polling and has overtaken him in early states like New Hampshire and South Carolina.

The debate, to be aired at 9 p.m. E.S.T., will be an opportunity for Mr. DeSantis to inject some momentum into his presidential campaign, which has been on a downward trajectory in the polls since early 2023.

At the end of January, Mr. DeSantis enjoyed about 32 percent support nationally in the GOP primary compared to President Trump’s 44 percent support. Since then, Mr. DeSantis has slumped to about 12 percent, according to FiveThirtyEight’s average of polls, while support for Mr. Trump has held steady at about 60 percent.

Mr. Newsom has himself warded off accusations from Republicans and some Democrats that he is waging a “shadow campaign” for president, in the words of Mr. DeSantis.

“He is running a shadow campaign. Even people in his own party are saying that a lot of Democrats want to move Biden out,” Mr. DeSantis told “Fox and Friends.” “I think it’s important that Republican voters get the sense that we may not be running against Biden.”

Mr. Newsom has mobilized his significant digital fundraising infrastructure to help support down-ballot Democrats nationwide, like a Democratic candidate in the Charleston, South Carolina, mayoral election, Clay Middleton, whose campaign raised some $17,000 thanks to a text sent out by a Newsom-affiliated fundraising group.

The debate also appears to be, for Mr. Newsom, an opportunity for him to try to take Mr. DeSantis down a notch, with Mr. Newsom criticizing Mr. DeSantis for going through with the debate when he is running a presidential campaign.

“I don’t know why he’s debating a governor of California. I mean, again, that is so disqualifying on his behalf,” Mr. Newsom said at the Fox News spin room after a recent GOP primary debate. “He put out an ad today, not about his debate for president [but] an ad about debating me. This guy is so off the ball that it really makes you wonder.”