In interviews, a range of officials and private analysts said that Mr. Trump was feeding many of the disinformation campaigns they were struggling to halt. And rather than travel the back roads of America searching for divisive issues — as three Russians from the Internet Research Agency did in 2016 — they are staying home, grabbing screenshots of Mr. Trump’s Twitter posts, or quoting his misleading statements and then amplifying those messages…

Multiple U.S. officials with access to the intelligence have said Mr. Trump has been doing the job of the Russian propagandists for them. Mr. Biden’s national security adviser when he was vice president, Antony J. Blinken, charged at a U.S. Chamber of Commerce forum on Tuesday that as a “leading consumer and purveyor of conspiracy theories,” Mr. Trump “seems to have suited up for the other side.”

Clint Watts, a former F.B.I. special agent and a fellow at the Foreign Policy Research Institute, said his review of the disinformation traffic showed that “the Russians in 2016 had to make false news stories or manipulated truths to power their narratives.”

“This time they’re not writing anything that’s not already said in U.S. space,” often by Mr. Trump himself, Mr. Watts added. “They must be flabbergasted and saying, ‘We really don’t need to work hard this time.’”