The stunning victory of the Brexit Party in Britain’s elections for the European Parliament is also a massive win for President Donald Trump — and a warning to the American political establishment about the potential political cost of undermining the agenda on which Trump was elected.

Nigel Farage’s party won 30.5% of the vote, and nine of ten regions in the UK; the Liberal Democrats won 20.9% nationally and came first place in London, but nowhere else; and both Labour and the Conservatives crashed.

The result is a victory for the Brexit policy that voters approved in 2016. It is an even more thorough repudiation of Britain’s political establishment, which hates Brexit and has tried to prevent its implementation. Those who favor the Remain position despaired of Labour’s wishy-washy stance, and were drawn to the Lib Dems’ “Bollocks to Brexit” approach. They may also have registered a protest against Labour’s tolerance of antisemitism.

Trump is a winner, in at least four ways. First, Farage is a political ally, who spoke at Trump election rallies in 2016, and whose campaign for British sovereignty provided a model for Trump’s own populist “America first” approach.

Second, the policy of the Trump administration is pro-Brexit, offering trade incentives once Britain leaves the EU. The president tweeted in April: “Too bad that the European Union is being so tough on the United Kingdom and Brexit.”

Third, the Brexit Party’s victory is only the latest in a series of conservative political victories — many of which came as a surprise to the media, including Benjamin Netanyahu’s victory in Israel in April and Scott Morrison’s re-election in Australia earlier this month. Across the world, political elites are telling voters to abandon nationalism — and voters are telling the elites to get lost. The result portends well as Trump gears up for his own re-election campaign next year.

Fourth, and most important, the Brexit Party’s win is a reminder that there is a price for defying the voters. The Tories came fifth in the EU elections — the worst result in their nearly 200-year history. They lost because Prime Minister Theresa May failed to implement the will of the electorate, and of Conservative Party voters in particular.

In the U.S., Congress has stalled Trump’s pledges on trade and immigration, fighting the border wall and blocking the USMCA. GOP voters have stuck with Trump, whom they know is fighting. But Americans remain disgusted with Congress.

There is a also parallel between the surge of the Lib Dems in the UK, and the rush of Democrats in the U.S. to embrace the far-left dogmas of “democratic socialism.” Voters on the left are looking for more determined opposition.

That could also shape the 2020 U.S. race. But for now, the Brexit Party’s success helps Trump and hurts his opponents.

Joel B. Pollak is Senior Editor-at-Large at Breitbart News. He is a winner of the 2018 Robert Novak Journalism Alumni Fellowship. He is also the co-author of How Trump Won: The Inside Story of a Revolution, which is available from Regnery. Follow him on Twitter at @joelpollak.