“If there’s an explosion or fire somewhere, Steve is probably nearby with some matches,” one of Steve Bannon’s former Breitbart News employees once said (admiringly). So it shouldn’t be surprising that Mr. Bannon, who was Donald Trump’s chief strategist, has arrived in Europe.

In late July, Mr. Bannon, the American political operative, announced his plan to establish The Movement, a foundation that he hopes will unite Europe’s far-right parties ahead of the May 2019 European parliamentary elections. Will he have the impact that he wants?

As Joshua Green writes in his book on Mr. Bannon, “Devil’s Bargain,” Mr. Bannon sincerely believed that right-wing Tea Party-style populism was a global phenomenon. What’s more, as he said at a conference in Budapest in May, “Brexit was a foreshadow of the 2016 Trump victory, and the populist nationalist revolt is about a year ahead in Europe than in the United States.”

But why Mr. Bannon has decided to pivot to Europe is less consequential than who his major ally on the Continent is: Prime Minister Viktor Orban of Hungary. If you’ve been closely following Mr. Bannon’s speeches in recent months (as I have), it’s easy to conclude that it is the far-right Hungarian leader whom the American populist provocateur not only admires but also seeks to help. Mr. Bannon has called Mr. Orban “Trump before Trump.” Mr. Orban, for his part, is looking to be as transformative and disruptive as the American president, and he hopes that the 2019 European election will help him build a majority in the European Parliament to, as he puts it, “wave goodbye not only to liberal democracy and the liberal nondemocratic system that has been built on its foundations, but also to the entire elite of ’68.”