Left-wing Labour Party leader Jeremy Corbyn saw his party mauled in Britain’s general election Thursday as its strongholds across the country fell to Prime Minister Boris Johnson’s Conservative Party -- a dramatic result that commentators on both sides of the pond are seeing as a warning to socialist-leaning Democrats ahead of the U.S. presidential election.

And for those who have openly cautioned about the party's drift to the left, the U.K. results were treated as nothing short of a wake-up call. A sign, for some, that even a populist incumbent as irreverent and contentious as Johnson could ride to victory when the alternative is an equally controversial leftist vowing massive government expansion.

The parallels were not hard to draw.

JOHNSON'S CONSERVATIVES PICK UP MASSIVE MAJORITY, WREAK HAVOC IN LABOUR HEARTLANDS

“Maybe this is the canary in the coal mine,” Democratic presidential hopeful Michael Bloomberg, who has tried to sell himself as a more electable alternative to candidates like Elizabeth Warren or Bernie Sanders since entering the race last month, told reporters Friday. “The public clearly wanted a change in the U.K. The change was much more rapid and [had] greater magnitude than anyone had predicted. And I think it’s sort of a catastrophic warning to the Democratic Party that you’re just going to have to have somebody that can beat Donald Trump, and that is not going to be easy.”

“Americans want change, but I think they don’t want revolutionary change,” the centrist billionaire said. “They want evolutionary change.”

Johnson’s Tories won 365 seats in Parliament’s lower chamber, with Labour picking up just 203. It hands the Conservatives their biggest majority since the days of Margaret Thatcher and marks the worst showing for Labour since the 1930s. The left-wing party was left shell-shocked after a night that saw once-safe seats in working-class areas turn Tory, with enormous swings that would have been unthinkable just a few years ago.

Seats in places such as Bolsover, Workington, Blyth Valley, Burnley, Wrexham and Stoke-on-Trent toppled one after another, each one yet another nail in the coffin of Labour’s hopes of ushering in a socialist government and preventing Britain’s departure from the European Union. It represented what many commentators are seeing as a realignment in British politics, as the Conservatives ripped up the electoral map and made gains in the North East, the North West and Wales in particular.

Corbyn announced that he would eventually step down, promising not to lead the party in another general election, but saying that would come after a “period of reflection.” He quickly tried to set the narrative that it was questions over Brexit, not his brand of hard-left policies, that had ultimately doomed the party.

"All those policies were extremely popular during the election campaign and remain policies that have huge popular support all across this country," he said. "However Brexit has so polarized and divided debate in this country it has overriden so much of a normal political debate and I recognize that has contributed to the results the Labour Party has received all across this country."

VARNEY: BORIS JOHNSON'S WIN SHOULD SEND A MESSAGE TO AOC, WARREN AND SANDERS

But while many of the seats that fell represent pro-Leave areas, polls suggested that it was Corbyn -- and his extreme brand of left-wing politics -- that was a more significant factor for Brits. Corbyn had taken over the party leadership in 2015 and dragged it to the left in a rejection of the kind of centrism embodied by three-term Prime Minister Tony Blair.

It’s a lesson that many in the U.K. and the U.S. are saying should be a warning for Democrats who may think that victory lies with an uncompromising agenda featuring government health care, immigration enforcement rollbacks and more. Democrats like Sens. Sanders, I-Vt., and Warren, D-Mass., have promoted far-reaching policies such as "Medicare-for-all" and a halt to deportations of illegal immigrants -- leading some to fear they may be out of step with the country.

“One lesson from the UK: if the Democrats don't stop their hard-left slide, they'll suffer the same fate as Labour,” commentator Andrew Sullivan tweeted. “If they don't move off their support for mass immigration, they're toast. Ditto the wokeness. Left Twitter is not reality.”

Former Daily Mirror editor Piers Morgan warned also about the Twitter bubble, and that Democrats should be careful about picking someone too far on the fringes.

“Bernie Sanders and Elizabeth Warren both share Jeremy Corbyn's socialist agenda and both appear to be as popular as him on Twitter,” Morgan said in an op-ed. “But Twitter's not the real world.”

He also drew comparisons between the British Left’s effort to thwart Brexit and the Democratic push to impeach Trump, rather than beat him at the ballot box.

“Those who voted for Brexit and Trump don't take kindly to their democratic vote being abused in this way and their retribution comes at the ballot box,” he said. “If people think Boris Johnson's earthquake was big, just wait until the Senate acquits President Trump and he uses that victory to storm to re-election.”

But if there is that kind of warning for Americans, it may be a message that meets significant resistance from activists hoping for their own version of a Corbynite revolution, and who may not be put off by the warning signs in Thursday's vote.

MSNBC host Chris Hayes pointed out that Corbyn is running in a way that many Democrats would like to see.

“One thing you can’t say about the Corbyn campaign was that he was ‘Tory lite’ or too neoliberal or too establishment. He ran unabashedly from the left in a way many leftists want Democrats to run here in the U.S.," he tweeted. But after some criticism he deleted it, saying it was a “bad take.”

But the message of the U.K. election had also resonated in the White House. On Friday, Trump suggested that just as the 2016 Brexit referendum foreshadowed his own presidential win a few months later, the 2019 U.K. election forecasts a win for him in 2020.

"I want to congratulate Boris Johnson on a terrific victory. I think that might be a harbinger of what’s to come in our country," he said. "It was last time."

Fox News' Paul Steinhauser and Kelly Phares contributed to this report.