The president’s public attacks on Jeff Sessions and James Comey, which came as he was also privately pressuring them, are being scrutinized.
WASHINGTON — For years, President Trump has used Twitter as his go-to public relations weapon, mounting a barrage of attacks on celebrities and then political rivals even after advisers warned he could be creating legal problems for himself.
Those concerns now turn out to be well founded. The special counsel, Robert S. Mueller III, is scrutinizing tweets and negative statements from the president about Attorney General Jeff Sessions and the former F.B.I. director James B. Comey, according to three people briefed on the matter.
Several of the remarks came as Mr. Trump was also privately pressuring the men — both key witnesses in the inquiry — about the investigation, and Mr. Mueller is examining whether the actions add up to attempts to obstruct the investigation by both intimidating witnesses and pressuring senior law enforcement officials to tamp down the inquiry.
Mr. Mueller wants to question the president about the tweets. His interest in them is the latest addition to a range of presidential actions he is investigating as a possible obstruction case: private interactions with Mr. Comey, Mr. Sessions and other senior administration officials about the Russia inquiry; misleading White House statements; public attacks; and possible pardon offers to potential witnesses.
None of what Mr. Mueller has homed in on constitutes obstruction, Mr. Trump’s lawyers said. They argued that most of the presidential acts under scrutiny, including the firing of Mr. Comey, fall under Mr. Trump’s authority as the head of the executive branch and insisted that he should not even have to answer Mr. Mueller’s questions about obstruction.
But privately, some of the lawyers have expressed concern that Mr. Mueller will stitch together several episodes, encounters and pieces of evidence, like the tweets, to build a case that the president embarked on a broad effort to interfere with the investigation. Prosecutors who lack one slam-dunk piece of evidence in obstruction cases often search for a larger pattern of behavior, legal experts said.