Fox News Headquarters in Midtown Manhattan. AP Photo/Mary Altaffer May 9, 2017, was a momentous day in American politics—unless you were watching Fox News.

Late that afternoon, President Trump stunned Washington by firing James Comey less than a week after the FBI director had testified to Congress about, among other things, the bureau's investigation into the Trump campaign's possible connections to Russia.

On the heels of that news came a rapid-fire series of revelations that cast the dismissal in lights ranging from sinister to farcical.

Trump claimed in his letter axing Comey that the latter had informed him "on three separate occasions" that Trump was not under investigation, which if true would have violated FBI protocol. Trump's White House sought to justify the firing, implausibly, as a response to Comey's handling of the Hillary Clinton email investigation—for which Trump had previously praised him.

Comey learned of his dismissal when he saw it on TV, and he thought at first it was a prank. White House Press Secretary Sean Spicer hid in the bushes—no, among bushes—to dodge questions from reporters. The night unfolded as if scripted by a screenwriter with a gift for dark humor.

And indeed, to anyone watching the news on CNN or MSNBC, here was a real-life, high-stakes drama wrapped in layers of deception and absurdity, unfolding minute by minute, one jaw-dropping development after the next. CNN

On Fox News, however, it was an altogether different story. Viewers of the nation's most-watched cable network were told first that Comey had "resigned," then that he had been fired and that the move was controversial.

But on show after show, from late afternoon into the night, the reasons for Comey's dismissal and the nature of the controversy were glossed over, and the juicy details that followed went unmentioned. The network's hosts almost unanimously treated Comey's firing as a fully justified and unsurprising development and accepted wholesale the White House's official explanation that Comey had been fired for cause. (Trump and his administration later changed their story multiple times.)

The widespread shock and criticism of the move from Democrats, pundits, and even some Republicans was explained away as a symptom of the Washington establishment's deep-seated enmity toward Trump even as the basis for it was never fully elucidated. The word "Russia" was studiously avoided.

On his 10 p.m. Eastern show, star opinion host Sean Hannity framed Comey's firing not in terms of its implications for Trump's White House but as an opportunity to reopen the investigation of Hillary Clinton's emails and put her behind bars at last.

For more than a decade, Fox News has dominated the cable news ratings with a potent mix of center-right daytime news shows and hard-right prime-time opinion shows—a menu devoured by the largely older, red-state Americans who make up the network's loyal audience.

The network finished 2016 as the most-watched channel in all of basic cable, and in the first months of 2017 it shattered its own ratings records, posting the most-watched quarter in cable TV history. Its remarkable run continued through the first week of this May when it bested center-left CNN and left-leaning MSNBC in key metrics every night.

But Comey's firing marked a turning point. The previous night, MSNBC had posted a rare win over Fox News in prime-time ratings among viewers age 25–54, the key demographic for advertisers.

The night he was sacked, Fox News plummeted to third in that metric, behind both MSNBC and CNN. Its fortunes have continued to flag since then.

Last week, for the first time since Bill Clinton was president, Fox News came in last of the big three cable news networks in weekly prime-time ratings for the 25–54 demographic. MSNBC beat it in total prime-time viewership, too.

What's behind the sudden shift? An obvious culprit might seem to be the turmoil within Fox News, which has ousted both its chairman and its biggest star in the past year amid sexual harassment scandals that also chased off several other prominent personalities. No doubt that has played a part.

Yet the network appeared to be weathering the storm until quite recently, with Tucker Carlson stepping into the slot long occupied by deposed ratings champion Bill O'Reilly and retaining his enormous viewership.