As a candidate, Donald Trump wasn’t shy about predicting the success of Brexit, the 2016 referendum that triggered Britain’s departure from the European Union and rocked the Continent’s politics.

But with Europe on the verge of another possible earthquake, President Trump has held his tongue about France’s upcoming presidential vote, surprising some who worried that he or his senior strategist, Steve Bannon, might somehow work to boost the controversial nationalist candidate Marine Le Pen.

Le Pen — an immigration hard-liner, European Union critic and ally of Russian President Vladimir Putin — is one of four candidates running neck-and-neck ahead of a Sunday vote that will winnow the French presidential field to two finalists for a May 7 runoff.

In a Thursday news conference with Italian Prime Minister Paolo Gentiloni, Trump dodged a question about the French vote, responding in general terms about the value of Europe.

“A strong Europe is very, very important to me,” Trump said. “We want to see it. We will help it be strong, and it’s very much to everybody’s advantage.”

That studied neutrality came hours after former President Barack Obama fielded a call from one of Le Pen’s centrist rivals, Emmanuel Macron. A spokesman said Obama was not making an endorsement but added that he is committed to France being “a leader on behalf of liberal values in Europe and around the world.”

Le Pen’s critics call her an opponent of liberal values and say that her victory would make Europe anything but strong — by dealing a potentially lethal blow to its key institutions and economy just as the perceived threat posed by Trump’s victory seems to be receding.

“The stakes for Europe are tremendous — this is a historic election,” said Jorge Benitez, a senior fellow at the Atlantic Council. A Le Pen victory, which many French analysts consider plausible though unlikely, could mean “the end of Europe as we've known it since World War II,” he added.

Le Pen has called herself “Madame Frexit” and wants a referendum on whether France should follow Britain out of the EU. “If France is out of the EU, it’s the end of the EU,” France’s ambassador to Washington, Gerard Araud, recently told CNN.

Le Pen has also called for France to at least partially withdraw from NATO.

She also has a supporter in Putin, who recently hosted her at Kremlin for a friendly photo-op. “It’s now the world of Putin, the world of Donald Trump,” Le Pen declared after the meeting. Western officials say Russian intelligence has sought to influence France's election in support of Le Pen.

The parallels between Le Pen’s candidacy and Trump’s had stoked speculation in Europe that the U.S. president might put his finger on the scale to assist her.

So did Le Pen’s December visit to the lobby of Trump Tower, which many French officials believe was just a publicity stunt. Trump officials say she was in a public area and that neither he nor Bannon met with her.

One Trump associate who has discussed European politics with him says that Trump understands that, as president, he can’t intervene in foreign elections.

“Even if there was some sympathy, there’s nothing a president can do. That would be very undiplomatic,” the associate said.

Trump also played it safe when he fielded a Tuesday phone call from British Prime Minister Theresa May shortly after she called a snap election for June 8. A White House statement said Trump “wished the British people the best of luck in their electoral process.”

Past presidents have telegraphed opinions about foreign votes with mixed results. Barack Obama visited London shortly before Britain’s Brexit referendum and made his preference clear without explicitly stating it. In 1996, Bill Clinton hosted Israeli Prime Minister Shimon Peres at the White House weeks before a vote in which Peres faced an insurgent Benjamin Netanyahu.

Neither president got the outcome he had hoped for. Brexit passed, an embarrassment to Obama. Clinton was rewarded with a deeply resentful counterpart in Netanyahu.

In some ways, a Trump-Le Pen alliance would seem natural. Both politicians have ridden a western populist movement fueled by resentment over wealth in equality and the perceived cultural and economic effects of immigration.

As a candidate, Trump branded NATO as an “obsolete” sinkhole for U.S. taxpayer dollars. He also described the EU as a bureaucratic drag on the Continent’s economic growth and an unfair trading partner.

Bannon, a major Brexit cheerleader, was even more zealous in his criticism of the EU. The Trump adviser has said the 28-member union, with its shared currency and open internal borders, erodes the identity and sovereignty of its member states.

After Trump’s election, the EU’s top official warned in an annual letter that the U.S., a supporter of European Unity for more than 70 years, now posed an outside “threat” to the union.

More recently, however, Trump and his top officials have adopted more conventional views toward Europe. On a February trip to Brussels, Vice President Mike Pence offered “strong commitment ... to continue cooperation and partnership with the European Union.”

And in a February 23 interview with the Financial Times, Trump called the EU “wonderful” and pronounced himself “totally in favor of it.”

Some experts believe that the twin surprises of Trump’s election and the Brexit vote have sparked a centrist backlash against Europe’s populist movements.

Trump and other top officials, including Pence and Defense Secretary James Mattis, have struck similarly reassuring notes about NATO. Last week he declared that the alliance is “no longer obsolete” — even as he continues to fixate on its budget.

European officials have also been consoled to see Bannon’s apparent loss of influence in the West Wing, where it was feared he would pursue a stridently anti-EU agenda.

Those shifts have not escaped the notice — or criticism — of Le Pen herself.

After Trump affirmed NATO’s relevance last week, she responded, “Undeniably he is in contradiction with the commitments he had made” as a candidate, adding: “I am coherent, I don’t change my mind in a few days.”

She also bashed his April 6 missile strike on Syria, complaining that Trump “had said he would not be the policeman of the world … but it seems today that he has changed his mind.”

If Le Pen emerges from Sunday’s runoff vote as a finalist, establishment European leaders will be alarmed but not panicked, so long as she faces the center-left Macron or the center-right Francois Fillon, both of whom are considered likely bets to defeat her in a May 7 election.

But political and market panic could erupt if Sunday’s winners are Le Pen and the left-wing Jean-Luc Melenchon, whom polls show Le Pen could overcome.

“It would be a disaster for the West if either one of them is elected,” said Jeremy Shapiro, a former assistant secretary of state for Europe and Eurasia in the Obama administration now at the European Council on Foreign Relations.

Melenchon, who left France’s socialist party complaining that it was too pro-business, is also an EU skeptic and wants to withdraw France from NATO. He also advocates much warmer ties with Moscow.

A Le Pen defeat would deflate a western populist movement already disappointed by the poor showing in March election of the Dutch right-wing Freedom Party, led by Geert Wilders, and which has seen its support in Germany wane ahead of summer elections there that will decide the fate of Chancellor Angela Merkel.

Some experts believe that the twin surprises of Trump’s election and the Brexit vote have sparked a centrist backlash against Europe’s populist movements.

Voters who one year ago may have cast what they thought was an anti-establishment protest vote may now act more cautiously — particularly given the disarray following both outcomes, said Thomas Wright, an expert on U.S.-European relations at the Brookings Institution.

“The various ‘exit’ and populist camps were damaged by Trump and Brexit because people saw that this could actually happen —and this is what it looks like,” Wright said.