Robert Mueller is under a tremendous amount of pressure these days. Republicans are painting him as a partisan intent on damaging the president for political reasons. It will be hard for him to refute that if it's thrown back at him at a trial.
Then there are Democrats. They have loaded all their faith onto him that he can bring down the president. He's under so much pressure he absolutely has to find something with which to charge Trump, whether it's some technicality involving some years old real estate transaction or whether it's some accidental misstatement that Mueller tries to call a "lie." If Mueller fails he'll be punished career wise once Democrats retake full control of the bureaucracy.
It's a no-win situation for Mueller.
12:25 PM 1/15/2018