Ms. Kelly is not the only Fox News veteran with a major role in the NewsNation debate.

Cherie Grzech, who produced 15 primary debates for Fox News before leaving in 2021, now runs NewsNation’s news and political programming. Chris Stirewalt, best-known as the Fox News analyst who defended the 2020 election night call for Arizona — a projection that enraged Mr. Trump, alienated viewers and led to Mr. Stirewalt losing his job — is NewsNation’s political editor.

Mr. Stirewalt said he believed in the mission of his new employer. “The shortest distance to securing a habituated audience is to cosset them and flatter them and to reinforce their prejudices,” he said. “The harder thing is to try to be aspirationally fair, and try to report and analyze honestly, not to reinforce existing opinions. It’s a substantially underserved market.”

This may be a counterintuitive business model, given the nation’s polarized state, but NewsNation is not alone in trying it out. Jeff Zucker, the former president of CNN, is aiming to acquire The Daily Telegraph, a London newspaper, in hopes of expanding its reach to center-right consumers in the United States.

Similar experiments have struggled. Shepard Smith, another anchor who left Fox News, created a straightforward newscast on the financial network CNBC in 2020; it was canceled after two years. Chris Licht, who succeeded Mr. Zucker at CNN, promised to dial back partisan opinion, but his programming efforts failed to jell and ratings plummeted.

Ms. Kelly, who has no qualms about expressing strong views, is more opinionated than her temporary partners at NewsNation. Eric Bolling, a former Fox News colleague who is now an anchor on Newsmax, said that would work to her advantage.

“She will be the biggest viewer draw of all Wednesday night,” Mr. Bolling wrote in a text message. “Unless Trump shows up!”