Fox News once devoted its 7 p.m. and 11 p.m. time slots to relatively straightforward newscasts. Now those hours are filled by opinion shows led by hosts who denounce Democrats and defend the worldview of former President Donald J. Trump.

For seven years, Juan Williams was the lone liberal voice on “The Five,” the network’s popular afternoon chat show. On Wednesday, he announced that he was leaving the program, after months of harsh on-air blowback from his conservative co-hosts. Many Fox News viewers cheered his exit on social media.

Donna Brazile, the former Democratic Party chairwoman, was hired by Fox News with great fanfare in 2019 as a dissenting voice for its political coverage. She criticized Mr. Trump and spoke passionately about the Black Lives Matter movement, which other hosts on the network often demonized. Ms. Brazile has now left Fox News; last week, she quietly started a new job at ABC.

Onscreen and off, in ways subtle and overt, Fox News has adapted to the post-Trump era by moving in a single direction: Trumpward.

amounted to an existential moment for a cable channel that is home to Trump cheerleaders like Sean Hannity and Laura Ingraham: the 2020 election.

Fox News’s ratings fell sharply after the network made an early call on election night that Joseph R. Biden Jr., the Democratic presidential nominee, would carry Arizona and later declared him the winner, even as Mr. Trump advanced lies about fraud. With viewers in revolt, the network moved out dissenting voices and put a new emphasis on hard-line right-wing commentary.

the network fired its veteran politics editor, Chris Stirewalt, who had been an onscreen face of the early call in Arizona for Mr. Biden. This month, it brought on a new editor in the Washington bureau: Kerri Kupec, a former spokeswoman for Mr. Trump’s attorney general William P. Barr. She had no journalistic experience.

opinion shows at 7 and 11 — with segments that lament “cancel culture” and attack Mr. Biden — are attracting bigger audiences than the newscasts they replaced. And the niche right-wing network Newsmax has failed to sustain its postelection audience gains.

In some ways, the Murdochs are making a rational business decision by following the conservatives who have made up the heart of the Fox News audience; recent surveys show that more than three-quarters of Republicans want Mr. Trump to run in 2024.

But under Roger Ailes, the network’s founder, who shaped its look and feel, Fox News elevated liberal foils like Alan Colmes, a Democrat who shared equal billing in prime time with Mr. Hannity until the end of 2008, and moderates like Mr. Williams.

“Roger’s view was you had to have some unpredictability and you had to challenge the audience; you couldn’t just be reading Republican talking points every night,” said Susan R. Estrich, a Democratic lawyer and former commentator on Fox News who negotiated Mr. Ailes’s exit from the network amid his sexual misconduct scandal.

Ms. Estrich recalled that Mr. Ailes had defended Megyn Kelly, the former Fox News host, when Mr. Trump, then a presidential candidate, attacked her in misogynist terms. Now, she said, “instead of trying to broaden their audience, Fox News is narrowing it and digging in.”