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.
