By Bernd Debusmann Jr and Anthony Zurcher for the BBC
Tucker Carlson has parted ways with Fox News abruptly with no indication his show on Friday would be his last. Photo: AFP
Tucker Carlson, the highest-rated cable TV host credited with setting the agenda for US conservatives, has left Fox News, the network announced.
In a statement, Fox News said it and Carlson had agreed to "part ways".
His last TV programme was Friday 21 April, the statement added. His primetime slot will now be hosted by a series of interim hosts until a permanent replacement is found.
The brief two-paragraph statement gave no reason for the abrupt decision.
On air, a Fox News anchor announced the departure with a tribute that thanked Carlson "for his service to the network".
The 53-year-old was not just a popular presenter, but also a historically influential one. His shows frequently set the agenda for conservatives and, by extension, the Republican party.
His programme offered a blend of populist conservative takes on issues ranging from immigration, crime, race, gender and sexuality, with "woke" ideology becoming a frequent target.
It made up four of the top 10 rated programmes on US cable TV, according to Nielsen data for the week 27 March to 2 April.
He was Fox News' top rated host, with more than three million viewers tuning in on an average night.
While the host often publicly agreed with Donald Trump, whose politics have transformed the Republican party in recent years, he would occasionally diverge from the former president's political views.
Fox News' competitors were quick to capitalise on Carlson's departure.
One rival network, Newsmax, said it had successfully attracted viewers from Fox News in recent months and Carlson's departure "will only fuel that trend".
The announcement of Carlson's departure comes just days after Fox News settled a defamation lawsuit from the voting machine company Dominion over its coverage of the 2020 presidential election.
In the lawsuit, Dominion argued that its business was harmed by Fox spreading false claims its machines were rigged against Trump.
The case prompted disclosures of text messages that showed Carlson's private views often contrasted with his on-air output.
His show, which aired in the coveted 8pm to 9pm EST slot, was cited repeatedly in court documents by Dominion's attorneys in their claim some of its output was defamatory.
Additionally, Fox News is also facing a lawsuit filed in March by former guest booker Abby Grossberg in which she accused Carlson of "vile sexist stereotypes". Fox News has counter-sued and said it would "vigorously defend these claims".
Carlson's latest interview with Trump came two weeks ago, despite disclosures in the Dominion case showing he had privately said of the ex-president: "I hate him passionately."
He also interviewed Twitter chief executive Elon Musk during what would become his final week on Fox News.
'Back on Monday'
His departure appears to have been sudden and came without the usual farewell that might be expected from a long-serving presenter.
A video shared on Twitter by journalist Aaron Rupar showed Carlson ending his show on Friday with the words "we'll be back on Monday".
Carlson first joined Fox as a contributor in 2009 before becoming a co-host of the Fox and Friends Weekend show between 2012-16, the year he began hosting the Tucker Carlson Show.
Before his Fox career began, Carlson also hosted shows on CNN and MSNBC, before founding the Daily Caller website alongside former Republican political adviser Neil Patel.
His tenure at CNN ended in 2005, just months after a heated on-air exchange with Daily Show host Jon Stewart.
Share price drops
The share price of Fox Corporation, owned by Rupert Murdoch, dropped 3 percent when Tucker Carlson's exit was announced. Photo: AFP / Getty Images
Fox Corporation, the Rupert Murdoch-controlled company that owns Fox News, saw its share price drop more than 3 percent in New York after the announcement.
That is comparable to the initial reaction when the company announced it would pay $US787m ($NZ1.2 billion) to settle the defamation suit brought by Dominion, though the shares in that case quickly recovered.
One way that Carlson's departure could affect Fox News financially is in its upcoming negotiations with cable networks over lucrative so-called carriage fees - paid to Fox by cable firms for carrying its network.
These fees are critical to the company's bottom line and it now enters negotiations with a vacancy in its most prominent time slot.
Another cable TV host, CNN's Don Lemon, announced on Monday that he had been "terminated" by CNN after 17 years, just hours after appearing on its recently re-launched morning show.
The embattled host had come under intense public criticism earlier this year for remarks about Nikki Haley, running for the Republican presidential nomination.
Additional reporting by Natalie Sherman and Michelle Fluery in New York
-BBC