That is most likely Paxton's only defense. There is a state statute, I think, that says if the public knows about the wrongdoing and elect him anyway, then they do not care.
There are two questions about that defense, as far as I know.First, what he did is against the State Constitution, and state statute can not over ride that. Second, did the people of the State of TX know all of the shady things he did.
Since Trump is not a law and order guy, of course he is against this. Paxton supported him, so any legal prosecution must be politcally motivated, even in a state as red as Texas. Must be all of those RINO's and Never Trumpers in the state. Trump also hates the precedent that an elected offical can be held responsible for wrongdoing while in office. How dare they? You don't see Putin or those guys in N Korea or China getting prosecuted for all of the crimes they committ? Why should Trump be any different? I mean why else would someone want to get elected if not to increase personal power?