A Russian influence operation in the United States “is something we’re looking very closely at,” said one senior intelligence official who, as others interviewed, spoke on the condition of anonymity to discuss a sensitive matter. Officials are also examining potential disruptions to the election process, and the FBI has alerted state and local officials to potential cyberthreats.

The official cautioned that the intelligence community is not saying it has “definitive proof” of such tampering, or any Russian plans to do so. “But even the hint of something impacting the security of our election system would be of significant concern,” the official said. “It’s the key to our democracy, that people have confidence in the election system.”

The Kremlin’s intent may not be to sway the election in one direction or another, officials said, but to cause chaos and provide propaganda fodder to attack U.S. democracy-building policies around the world, particularly in the countries of the former Soviet Union…

After Senate Minority Leader Harry M. Reid (D-Nev.) ended a secure, 30-minute phone briefing by a top intelligence official recently, he was “deeply shaken,” according to an aide who was with Reid when he left the secure room at the FBI’s Las Vegas headquarters.