Supporters of Austrian far-right Freedom Party presidential candidate Norbert Hofer hold masks with Hofer’s face during a September rally in Vienna. (Leonhard Foeger /Reuters)

Attendees gathered this month inside Vienna’s opulent Grand Hotel for an extraordinary event billed as the “New Anti-Semitism Conference.” The Israeli superspy who hunted down war criminal Adolf Eichmann flew in for the occasion, timed to commemorate the 1938 night when the Nazis stormed synagogues and Jewish businesses.

What made the event truly remarkable, however, was its sponsor: Austria’s Freedom Party — a movement of anti-immigrant, right-wing nationalists founded in part by former Nazis and now on the cusp of capturing this nation’s presidency.

“They are one of the most pro-Israel parties in Europe,” insisted Michael Kleiner, a conference panelist and former member of the Israeli parliament.

Newly energized by the victory of Donald Trump in the U.S. presidential race, anti-establishment forces on the political right are pushing into the mainstream on both sides of the Atlantic. As they do, many are seeking to neutralize one of their oldest and most debilitating labels: that they are anti-Semites.

In the United States, top Trump adviser Stephen K. Bannon is fending off accusations of anti-Semitism even as archconservative Jewish voices rally to his defense. Using the forum of Breitbart News — the website that Bannon ran and is described as “the platform for the alt-right,” a white-state movement often espousing anti-Semitic views — they have called him an “honorary Jew” and a man without “an Anti-Semitic bone in his body.”

Many far-right parties in Europe are celebrating the presidential victory of Donald J. Trump. (Jason Aldag,Ishaan Tharoor/The Washington Post)

In France, the Netherlands and Sweden, right-wing nationalists are counterprogramming decades of deeply ingrained anti-Semitism in their ranks. Critics say some hard-right parties in Hungary and Greece remain hotbeds of anti-Semitism. But as left-wing parties in Europe press for boycotts of Israel over its treatment of Palestinians, many populist nationalists in Europe — at least in public — are pledging Israel their full support.

Nowhere has the rebranding been more effective than here in Austria. Freedom Party candidate Norbert Hofer is facing a center-left opponent in a rerun of May’s presidential election — which Hofer narrowly lost — after a successful court challenge by the far right. Ahead of the Dec. 4 vote, Hofer and his opponent are in a statistical tie. Although the job of Austrian president is traditionally ceremonial, it comes with ambiguous powers that Hofer has vowed to amp up. A Freedom Party victory would make Hofer the first far-right head of state in Western Europe since the demise of Nazi Germany.

His victory would also mark a huge step forward for the Freedom Party, founded in the 1950s and initially led by a former officer of the Nazi SS. Today, it is headed by Heinz-Christian Strache, who took over after a 2005 split with Jörg Haider — its former chief, known for thinly veiled flattery of Adolf Hitler. Strache is angling for Austria’s top job — chancellor — in elections that could be held as soon as next year.

Its leadership insists that not only has the party purged its ranks of anti-Semites but now it also shares a common cause with Israel and the Jewish people: controlling the spread of Islam. Indeed, the Freedom Party is pledging to protect ethnic “Judeo-Christian” culture on the continent by stopping Muslim immigration and imposing more surveillance on Austrian mosques. That mission, it argues, has become all the more urgent given the recent arrival in Europe of nearly 1 million refugees from the Middle East.

“Islam is not a part of Austria,” Hofer said at the anti-Semitism conference, while seated near the famed Israeli Nazi hunter Rafael Eitan. “By the year 2050, 50 percent of the children [in Austria] under 12 will be Muslims. . . . The kind of politics that is permitting a changing face of Austria and Europe has to be opposed.”

His campaign to court Jews and Israelis has gone all the way to the Temple Mount, where Hofer made a pilgrimage during a 2014 visit to Jerusalem. In April, Strache laid a wreath at Jerusalem’s Yad Vashem Holocaust memorial.

The Israeli government — still cautious about the Freedom Party’s far-right roots — did not officially greet the party’s delegates. But David Lasar, a top Hofer adviser who is Jewish, said private meetings took place in April between Strache and some Israeli government ministers. He declined to give names.

Lasar, who calls the Freedom Party a rare friend for Israel in Europe, portrayed Muslims in Austria as the real threat to Jews. He cited a spike in anti-Semitic incidents. In 2015, such incidents jumped 82 percent to 465 cases, including two physical attacks, according to Austria’s Forum Against Anti-Semitism. The forum did not break down how many incidents were attributable to Muslims but said it was concerned about an “increase in Islamist-motivated violence.”

The Freedom Party says one of Hofer’s first trips if he wins will be an official visit to Israel. On Friday, Strache issued an impassioned plea for the Austrian government to help Israel combat a sudden rash of fires there, including some allegedly set by Palestinian nationalists.

“The new anti-Semitism in Austria, in Europe, is being imported and spread by Islam,” Lasar said. “It’s important that Austria maintains a Judeo-Christian tradition. Islam is not a part of that.”

The Jewish community in Austria today — numbering slightly more than 8,000 people — is a shadow of the pre-World War II population of about 185,000. Freedom Party officials say that Jews represent so few votes now that the party could hold no political motive other than a genuine desire for rapprochement.

Yet critics decry the effort to court Jews as little more than window dressing designed to portray the party as reformed, thus appealing to non-Jewish centrists. It is also, critics say, meant to obfuscate what is still a core racist message, this time aimed at Muslims. Across Austria, Freedom Party candidates have peppered the landscape with billboard slogans such as “Love for the Homeland and Not Moroccan Thieves” and “New Apartments Instead of New Mosques.”

Austrian Jews are divided over how to react. Some — like Michael Kaner, a 28-year-old Vienna Web designer — are backing the Freedom Party. Although his family — especially his mother — is strongly against his decision to vote for Hofer, Kaner said that he is deeply concerned by reports of Muslim harassment of Jews and is “tired” of left-wing Austrian politicians railing against Israel.

Hofer, on occasion, still wears a lapel pin of a blue cornflower — a symbol of Germanic nationalism once used by the Nazis. He also attends a fraternity ball in Vienna long rooted in nationalist thought. But Kaner said that he is unconcerned by such acts.

“They are not neo-Nazis. Should we ask them to stop wearing Hugo Boss clothing, too, because the Nazis wore it?” he said. “I know other Jews who are voting for Hofer, too, but they don’t want to admit it.”

Jewish critics, however, are blasting Austria’s main Jewish cultural body for not doing more to stand up to the Freedom Party’s targeting of Muslims.

“This is a question of morality for the Jews in Austria,” said Karl Pfeifer, an Austrian Jewish journalist and author. He fled the Nazi invasion of Austria as a child and returned after World War II.

“Any party that is inciting against a minority group cannot be trusted,” he said. “Nobody should understand that more than us.”

Critics also call the party’s move to cultivate better ties with Jews little more than a whitewash. In 2011, Hofer told a far-right German publication that the scientist Konrad Lorenz — who espoused ideas almost indistinguishable from Nazi race theory — was one of his role models. Earlier this year, the German daily Bild confronted Hofer with a photograph showing his aide Rene Schimanek as a young man at a neo-Nazi event carrying what appeared to be a baton.

Hofer acknowledged that the photo was real but said Schimanek “has never been indicted or convicted” for the incident. He added that it had occurred “30 years ago and you shouldn’t use something like this against someone.”

Under Strache, the Freedom Party has indeed moved to rid its ranks of anti-Semites, ousting, for instance, one prominent politician last year for apparently agreeing with an article blaming “Jews worldwide” for Europe’s refugee crisis. This year, the party voted in favor of building a memorial in a village where the Nazis killed about 10,000 Austrian Jews.

Yet in 2012, Strache briefly posted a cartoon on his Facebook page depicting a fat banker with an exaggerated nose that was widely criticized as anti-Semitic. And anti-Semitism still flourishes, critics say, on the party’s fringes. They cite far-right Austrian magazines like Die Aula, in which the Freedom Party has advertised. Last year, the magazine published an article claiming local Austrians “suffered” after the liberation of the Nazi’s Mauthausen concentration camp because freed prisoners engaged in “robbing, pillaging, murdering and raping.”

“The right has discovered its love for Judaism,” said Ariel Muzicant, an Austrian Jew and vice president of the World Jewish Congress. Calling the overtures “bizarre,” he added, “we are repudiating such attempts.”

Stephanie Kirchner in Berlin and Ruth Eglash in Jerusalem contributed to this report.