Britain’s vote to leave the E.U. invigorated Trump supporters in Congress. Photographer: Matthew Lloyd/Bloomberg

Donald Trump’s supporters were invigorated Friday by the shocking news that British voters opted to leave the European Union.

They even called on American voters to follow Britain’s lead and elect Trump — who has said “America First” will be the “major, overriding theme of my administration” — as their president in November.

“The failed European Union experiment, and Great Britain’s rejection of it, must serve as a wake-up call for all of us in America,” said Sen. Jeff Sessions (R-Ala.), the first senator to endorse Trump. “I believe the American people too will choose independence this November.”

The surprising victory of the “Leave” campaign demonstrated the power of populism in a dissatisfied electorate. Trump has capitalized on a similar force in the U.S., using it to knock out more politically-seasoned competition in the GOP primary and counting on it to drive supporters to the polls in November.

“I really do see a parallel between what’s happening in the United States and what’s happening here,” Trump said Friday in a press conference in Scotland. “You’re going have this happen more and more…It’s happening by the fact that I’ve done so well in the polls.”

[Trump’s Brexit news conference was beyond bizarre]

Electoral college math suggests Trump will have a harder time winning the White House than “Leave” voters had winning a close referendum. But some members of Congress warn the “elite” should not discount the demands of disgruntled voters.

“The result of this referendum should remind leaders in Washington, London, Brussels and across Europe that our citizens are dissatisfied with stagnant economies, declining wages, uncontrolled migration, rising crime and terror attacks at home,” said Sen. Tom Cotton (R-Ark.), who has advised Trump on a few occasions and has not ruled out serving in his administration.

Some congressional Democrats suggested the Brexit vote is a cautionary example the U.S. should avoid repeating.

Senate Foreign Relations Committee senior Democrat Ben Cardin (Md.) said he was “disappointed by the outcome of the referendum,” particularly when the U.S. and Europe must present a united front against a resurgent Russia and terrorist threats from the Islamic State.

“This act of self-inflicted instability was fueled, in no small part, by the anti-immigrant, isolationist populism we’re seeing on the rise throughout the world and even here at home,” House Minority Whip Steny Hoyer (D-Md.) said in a statement Friday.

The Brexit vote had an anti-establishment allure that gripped even Republicans who say Trump “scares” them.

“The decision by the British people to leave the EU is a rejection of centralized power and unaccountable bureaucracy, a sentiment widely shared by many Americans,” said Sen. Mike Lee (R-Utah) in a statement. “Now more than ever we must respect the will of their people.”

For members of Congress, Britain’s decision to part ways with the E.U. is not just a chance to draw political parallels between old allies.

There is a clear role for Congress to play in the U.S. response: Washington and London now have to strike a new free trade agreement, and Congress has to approve it.

Cotton stressed the Obama administration should start negotiating a free-trade agreement with the U.K. “now,” while Lee said he would introduce legislation to let the U.S. and U.K. operate in the spirit of current arrangements “until new bilateral agreements can be negotiated.”

Economic cooperation has traditionally been a major part of U.S.-U.K. relations, and House Speaker Paul Ryan (R-Wis.) is a champion of free trade, arguing in the House GOP’s national security strategy that trade can “play a key role in strengthening U.S. alliances.”

But free trade has taken political hits recently, as lawmakers bitterly divide over the Trans-Pacific Partnership,  a massive agreement that Congress may vote on after the election.

Some lawmakers are using Brexit as an excuse to rail against TPP again and warn against all international partnerships.

“We must remember that the European Union began as a seemingly benign economic agreement,” Sessions said, adding that Clinton promoted the TPP as “the gold standard” of trade deals as part of her “globalist agenda.”

TPP isn’t the only “globalist” arrangement Trump and his supporters have taken shots at. Trump himself has been dismissive of the United Nations and called NATO “obsolete.”

Republican leaders have rushed to soften his message. The House GOP’s national security blueprint stressed NATO countries should spend more on defense so the organization would not “fall into disrepair, or worse, irrelevance.” Senate Foreign Relations Committee Chairman Bob Corker (R-Tenn.) expressed similar sentiments this week.

But both Corker and Ryan were exceedingly measured Friday in their response to the U.K.’s decision to leave the E.U.

“A free people should choose their own way, and we respect the British decision to leave the European Union,” Corker said in a statement, urging focus on bilateral trade and security cooperation, and adding the U.S.-U.K. “close partnership will endure.”

“I respect the decision made by the people of the United Kingdom,” Ryan said, calling the U.K. “an indispensable ally” and ensuring “that special relationship is unaffected by this vote.”