The words appearing most frequently in the Twitter biographies of the attackers were “Trump,” “nationalist,” “conservative” and “white.” Many of the owners of the 1,600 Twitter accounts were anonymous, though at least two are prominent white supremacists: Andrew Anglin, the founder of the website The Daily Stormer, and Lee Rogers of the Infostormer.

The report was careful not to suggest that the Trump campaign “supported or endorsed” the anti-Semitic attacks, but noted that many had been sent by his supporters.

But some of the targets said that by evoking hostility toward minorities, Mr. Trump’s campaign had inspired and emboldened white nationalists and others to engage in acts of digital aggression toward “others” — including Jews — and toward Jewish journalists in particular.

“The best analogy I can give is that the campaign turned over a rock and a lot of stuff began crawling out from under it,” said John Podhoretz, the editor of Commentary magazine. “There were these code words and dog whistles that let it appear that people who had been doing things in the shadows could now start marching forward.”