The problem is that Jared or someone gave Trump bad advice on Rosenstein, who Dems know is on their side, so they’d try to stop any replacement for Sessions, and probably with McCain, Corker & Flake helping.
I think the answer is obvious.
DJT needs to pressure Sessions unmercifully to fire Rosenstein and any replacements until we get a good #2 man in place. At that point firing Sessions becomes a possibility. The RATs will not block a new AG in the acting AG is no longer favorable to them.