President Trump put fresh pressure on the second-highest-ranking  official at the Justice Department on Friday, raising concerns among the  president’s critics that Rod J. Rosenstein could be in danger of being fired, while others argued that if he stays he should recuse himself  from his role overseeing the special-counsel probe that has engulfed the White House. “I am being investigated for firing the FBI Director by the man who told me to fire the FBI Director! Witch Hunt,” the president said on Twitter.