If they decide the President is immune from state subpoenas or prosecution, it would be something they created just for Trump. Likewise, if they decide the President can pardon himself or anybody for state crimes.
Even the decision about giving his tax returns to congress, would be the Supreme Court going directly against a clear and simple law passed by Congress. Thee is no mention in that law about why the congressional committees are asking for them. The Supreme Court is supposed to interpret the laws, not make new ones.
How does it go? "elections have consequences."
Like a packed court.
This is why I laugh people who act like elections don't matter, even if you don't like either candidate.