– Britain and the U.S. have often seemed lashed together amid the populist storms of the last few years — Brexit and the Trump White House echoing and amplifying each other across the Atlantic. But in one respect they have radically diverged.

In London, rebels in the Conservative Party staged a dramatic insurrection against Prime Minister Boris Johnson, blocking his plan to withdraw Britain from the European Union, even without a deal. In Washington, scarcely a handful of Republicans have stood up to President Donald Trump, even when he has flouted party orthodoxy on issues like trade, immigration and the deficit.

The Tory party’s revolt and Johnson’s ruthless purging of the rebels are reverberating through British politics, threatening his hold on power. For dispirited Republicans, though, this British revolution has become an object lesson.

Conservative rebels “showed courage and principled concern about the impact of bad policy on the U.K. economy,” said Daniel Price, who served as an economic adviser to President George W. Bush. “This contrasts with congressional Republicans here who have mostly been meek, mute or complicit.”

The uprising in Westminster came even though British political parties enforce discipline far more strictly than their U.S. counterparts. Johnson punished the 21 renegades by throwing them out of the party. Trump can ostracize GOP dissidents and dry up their funding, but he cannot banish them from the party.

Much of the difference, experts said, has to do with the magnitude of the crisis in each country. The Tories who broke with Johnson regard his vow to take Britain out of the E.U. on Oct. 31 as so reckless that it poses a dire threat to the nation — one that would wreak economic havoc and sunder both their party and British society.

Analysts warn that a no-deal Brexit, one in which Britain abruptly leaves Europe without transitional arrangements on trade or borders, will lead to food and medicine shortages, trucks backed up on both sides of the English Channel, and the threat of violence in Northern Ireland, where a hard border could reignite sectarian ­troubles.

“To deliver Brexit like this is to create a poison pill that for 40 years will divide this country straight down the middle,” Rory Stewart, a Conservative Party rising star, told the BBC.

Stewart, who challenged Johnson for party leadership in June, learned of his expulsion via a text message Tuesday just minutes before GQ magazine honored him as its politician of the year.

While many Republicans deplore Trump’s divisive language and erratic conduct, few accept — at least publicly — the argument that he poses a comparable threat to the U.S. However distasteful they find him, Republicans largely back his agenda, whether it is the appointment of conservative judges, the passage of tax cuts, or deregulation.

They are even willing to tolerate his overturning of traditional GOP priorities such as free trade, in part because of the damage they fear a vengeful Trump could do to them at the polls. Trump has thoroughly taken over the Republicans, remaking the party of Lincoln in his image and institutionalizing policies that, only a few years ago, would have seemed extreme to them.

Johnson wants to engineer a similar takeover of the Conservatives, purifying the party of Churchill and Thatcher so it can repel challenges from the hard-core pro-Brexit movement, which now has its own competing party. If he clings to power, a more radicalized Tory party could yet emerge.

But Johnson offers little to supporters beyond a promise to leave the E.U. next month. His other policies — tax cuts, more money for the police, tighter immigration rules — are standard Conservative fare. Several of his rivals for the party leadership ran on substantively similar platforms.

While Johnson’s flamboyant image and populist appeals bear a surface similarity to Trump, he has not mobilized a grassroots political movement anywhere near that of Trump. Nor does he enjoy the prerogatives of a system with a fixed four-year term. This past week, he wasn’t even able to call an election without the assent of the opposition Labor Party.

“Trump got elected; he got through the fires,” said former GOP Sen. Alan Simpson of Wyoming. “Unkempt Boris just showed up on the scene. You can rough up a guy like that.”