The latest example of speculation is in one of the documents that Airman First Class Jack Teixeira, whom federal agents arrested this month, is accused of leaking. It asserts that a member of Ukraine’s parliament, Yelizaveta Bohutska, claimed to know about a plan by Russian officials to undermine their own military to “sabotage” Mr. Putin.
Ms. Bohutska said the plan was to engineer a military setback by March 5, “when Putin was allegedly scheduled to start a round of chemotherapy and would thus be unable to influence the war effort,” the document states.
Ms. Bohutska disclosed the plot on Feb. 17 to Andriy Yermak, the chief of staff to Mr. Zelensky, according to the document. Ms. Bohutska, it added, had “received the information from an unidentified Russian source with access to Kremlin officials.” Neither Ukrainian official responded to requests for comment.
The document did not indicate how the United States knew about the conversation, but the leaked reports confirm suspicions that the Biden administration has been surveilling Ukraine’s government and other allies.
Subsequent events have not borne out the claims. While Mr. Putin made no public appearances on March 5, according to a Kremlin archive of his activities, that date fell on a Sunday, when he would usually not be active in public. And Mr. Putin had numerous meetings the following week.
Nor is there evidence that Russian forces experienced a surprising setback around that time.
Social media sleuths have long seized upon videos of Mr. Putin’s public appearances, claiming to identify changes in his appearance, speech, gait, or posture as evidence of faltering health.
“Fiction and falsehood,” the Kremlin spokesman, Dmitry Peskov, said last April when asked about the cancer rumors, according to a post on Telegram by the veteran Russian journalist Alexei Venediktov.