For Mr. Heimbach is far from alone in his esteem for Mr. Putin. Throughout the collection of white ethnocentrists, nationalists, populists and neo-Nazis that has taken root on both sides of the Atlantic, Mr. Putin is widely revered as a kind of white knight: a symbol of strength, racial purity and traditional Christian values in a world under threat from Islam, immigrants and rootless cosmopolitan elites.

“I’ve always seen Russia as the guardian at the gate, as the easternmost outpost of our people,” said Sam Dickson, a white supremacist and former Ku Klux Klan lawyer who frequently speaks at gatherings of the so-called alt-right, a far-right fringe movement that embraces white nationalism and a range of racist and anti-immigrant positions. “They are our barrier to the Oriental invasion of our homeland and the great protector of Christendom. I admire the Russian people. They are the strongest white people on earth.”…

Mr. Spencer, who held a much-discussed conference in Washington in November, produced a video last year in which he claimed that “an understanding” between Mr. Trump and Mr. Putin might bring together Slavic and American Caucasians and eventually “foretell a unified white world.” This summer, he echoed those remarks when he told The Nation magazine, “I think we should be pro-Russia because Russia is the great white power that exists in the world.”

In an interview this past week, Mr. Spencer — he made headlines at his conference by shouting “Hail Trump!” — offered a more measured version of this sentiment, referring to Mr. Putin as “a normal leader in an abnormal world.”