Chuck Grassley has said that a new attorney general won’t be confirmed by the Senate, and it’s been made clear, by Ben Sasse among others, that the Senate is not going into recess to avoid creating the opportunity for a recess appointment. This means if Trump wants to fire and replace Sessions with someone who isn’t recused, he’d have to rely on an acting attorney general, and someone who is not the naturally next-in-line, Rod Rosenstein. I guess this is possible, but it would be a truly jerry-rigged scheme that would create an enormous political backlash. The Senate obviously can’t stop Trump from firing Sessions, but it has made it harder.