“He will fire her if she doesn’t perform as he wishes.”
If this were a normal situation, yes. Perception is real tough to control though.
He can’t go through 3 campaign managers in 3 weeks without creating some pretty negative perceptions. He has to stick it out with her, take the good and bad, for a while.
I think your time frame is mistaken.
Lewandowski was replaced partly due to the incident with a news reporter. (Which turned out to be false.)
Manafort was hired to get representatives during the primaries. Manafort is still on staff as a consultant according to my understanding.
Conway and Bannon have been given specific tasks to do.
Think of Trump — he hires people to get one thing done and then lets them go or has them stay on as a consultant. It’s different from what we are used to in a campaign.