ROME — Conventional wisdom says that the European right — amid widening support and buoyed by strong election results this summer — will be further strengthened if Donald Trump wins the U.S. presidential election.

One trouble with the theory, however, is that it’s not clear which European right the Republican nominee would be working with if he returns to the Oval Office after Nov. 5’s vote.

“When people ask about the European right, I ask them, ’Which kind of right?’” Antonio Villafranca, vice president of research with the Italian Institute for International Political Studies (ISPI), a Milan-based think tank, noted in an interview.

While European transatlanticists greet the prospect of a second Trump administration with a mixture of dread and horror, not everyone on the continent is bracing for disaster. Many of Mr. Trump’s political themes — notably a focus on illegal immigration, traditional-values populism and a distrust of global elites — have proven politically potent in countries from Sweden and the Netherlands to Spain and Italy.

Combined, far-right and conservative parties have more influence in Europe than at any time in decades. They are part of the ruling coalition in seven European Union member states (possibly soon to be eight, following elections in Austria in which a once-shunned far-right party was the single biggest vote-getter), while in multiple others they have the parliamentary power to shape major legislation.

NATO’s new secretary-general, former Dutch Prime Minister Mark Rutte, was chosen in part earlier this year because he built a workable relationship with Mr. Trump during his first four years in the White House.

Comfort Ero, president of the International Crisis Group think tank, wrote in a recent analysis that a Trump victory would provide a major boost to “the morale of far-right European politicians working against a stronger, more integrated Europe.”

But a look beneath the hood still shows big differences between the different camps. Europe’s conservative forces are by no means a monolith.

Mr. Villafranca pointed to the differences between the traditional European fiscal conservatives, the reformist parties headed by Italian Prime Minister Giorgia Meloni, nationalists like the French opposition head Marine Le Pen, European Union skeptics like Viktor Orban of Hungary, Brexit architect Nigel Farage in the U.K., as well as smaller and more extreme parties that dot the continent’s political landscape.

“In general, all the European right-wing parties should — and I am very careful to use the conditional ’should’ — look favorably on Trump’s election,” Mr. Villafranca said. “But there is also a sense of trepidation among them in certain policy areas when it comes to a new Trump administration.”

Mirror agendas

Many of Mr. Trump’s political priorities are mirrored by European conservatives. Most oppose mass migration, for example, and they appeal to nationalist pride and the support of traditional values. They’re also largely skeptical of centralized power, which for European conservatives means the centralized Brussels bureaucracy of the European Union.

But one aspect of another Trump presidency that worries Europeans on the right as well as on other points of the political spectrum is related to trans-Atlantic relations and security. Mr. Trump has criticized NATO member states that spend too little on defense and said the U.S. could not be counted on to come to their defense if they are attacked as required by NATO’s Article 5, which focuses on collective defense.

In comments early this year that ricocheted around the continent, Mr. Trump drew a tough line against NATO members who he said had failed to pay their share towards the alliance’s collective defense.

“’You didn’t pay? You’re delinquent?’” Mr. Trump said at a South Carolina rally in February, recounting what he said was a conversation he had had with an unidentified NATO leader complaining about Mr. Trump’s tough line.

“’No, I would not protect you. In fact, I would encourage [the Russians] to do whatever the hell they want. You gotta pay. You gotta pay your bills,’” Mr. Trump recalled saying.

It’s also likely Mr. Trump would cut off or scale back military and economic aid to Ukraine in order to force the country to negotiate with Russia. If Ukraine falls to Russia, leaders in Eastern Europe worry that an emboldened President Vladimir Putin could set his sights on their territories.

“Whether the U.S. remains an active player in European security, whether it continues to provide aid to military aid to Ukraine, and also how the election plays out in our own democracies, those are the key factors Europeans are considering,” Michal Baranowski, managing director with the German Marshall Fund East and the organization’s regional director for Poland.

Elusive consensus

But even amid these worries, there is no consensus among European leaders on how to deal with Mr. Trump in a second term.

Mr. Orban in Hungary in particular has formed a mutual admiration society with Mr. Trump, who name-checked the Hungarian conservative in his debate with Democratic nominee Vice President Kamala Harris as an international leader he could work with.

Mr. Orban was the only world leader to visit Trump at Mar-a-Lago in July after they gathered in New York for the annual United Nations General Assembly gathering. To the consternation of many of his fellow EU leaders, he has called the former U.S. president “a man of peace.”

Mr. Trump is trying “to pull the American people back from a post-nationalist liberal state to a nation-state,” Mr. Orban said this summer, saying that was why left-leaning elites on both sides of the Atlantic have attacked him.

Mr. Orban is also the European leader who has cultivated the closest ties with Russia’s Mr. Putin and has worked to slow or block aid to Ukraine within the European Union, a view that most likely aligns with Mr. Trump’s view.

But depending on how Tuesday’s close American election turns out, Mr. Orban may not be as big an outlier in a second Trump administration.

Ms. Meloni, in Italy, has been one of Ukraine’s most reliable allies in Europe and has even pledged to host the 2025 edition of the global conference to rebuild the country after the conclusion of the war with Russia. But there is already speculation in Europe that Ms. Meloni and other leaders could soften their support for Ukraine to get closer to the Trump White House.

According to Sudha David-Wilp, a Berlin-based senior fellow with the German Marshall Fund, there is also the possibility that European leaders could use a Trump victory as an excuse to distance themselves from Ukraine, in the face of polls showing growing public weariness with the heavy bills that have come with supporting Kyiv in the face of a relentless Russian offensive.

“We shouldn’t underestimate the prospect that a number of European leaders could see as a political opportunity, a deal where they could scapegoat Donald Trump for the future of Ukraine,” Ms. David-Wilp said. “You could imagine that rather cynically, some European leaders would be happy to say that the loss of Ukraine is a result of Donald Trump’s policies, and that they are not responsible for it.”

Mr. Orban is making little secret of his hopes, announcing on social media this week he had called Mr. Trump and wished him “best of luck for next Tuesday.”

“Only five days to go,” he posted. “Fingers crossed.”