In 2016, American intelligence agencies delivered urgent and explicit warnings about Russia's intentions to try to tip the American presidential election – and a detailed assessment of the operation afterward – thanks in large part to informants close to President Vladimir V. Putin and in the Kremlin who provided crucial details.
But two years later, the vital Kremlin informants have largely gone silent, leaving the C.I.A. and other spy agencies in the dark about precisely what Mr. Putin's intentions are for November's midterm elections, according to American officials familiar with the intelligence, The New York Times wrote.
The officials do not believe the sources have been compromised or killed. Instead, they have concluded they have gone to ground amid more aggressive counterintelligence by Moscow, including efforts to kill spies, like the poisoning in March in Britain of a former Russian intelligence officer that utilized a rare Russian-made nerve agent.
Current and former officials also said the expulsion of American intelligence officers from Moscow has hurt collection efforts. And officials also raised the possibility that the outing of an F.B.I. informant under scrutiny by the House intelligence committee – an examination encouraged by President Trump – has had a chilling effect on intelligence collection.
"The Russians kicked out a whole bunch of our people," said John Sipher, a 28-year veteran of the C.I.A. who served in Moscow in the 1990s and later ran the agency's Russia program. "Our station in Moscow is probably really small now and they are under incredible surveillance."
"The Russians are very focused and upset," Mr. Sipher said. "They have shown they are willing to kill sources."