Legally, what can the Governor do about it? The Senate is a Federal office.
The party will talk Fetterman (or his wife) into resigning, so Shapiro can appoint . . . Fetterman’s wife.
Doubttful, she doesn't have any party earned juice and paid no dues.
I think naming his wife will be harder than one thinks. There are a lot of Pa. Dems who likely believe thry have a lot more cred and right to take the seat and and Shapiro may be far more beholden to them than to Fetterman’s wife.
That was always the plan.