If Mueller goes on a witch hunt and investigates more than obstruction and Russian collusion or if anything leaks from his staff about his investigations such as Trump tax records, Trump will try to fire him, and rightly so.
I find this whole situation to be rather amusing, the irony is just so thick.
First, it is pretty much agreed on both sides that Trump did not collude with the Russians. So the fact that the Dems are now pushing obstruction of justice into the collusion probe bags the question, how could Trump obstruct an investigation that had no merits to begin with? If the collusion investigation was not going to go anywhere, how could one obstruct that?
Furthermore, considering no one now thinks he colluded, it can be assumed Trump is innocent of this charge. If he is innocent, he would have known he was innocent, so why would he even bother to try and obstruct. It makes no sense.
Of course some here will say a lot about Trump makes no sense and that he did it just to do it. That argument could be valid, but if Trump is truly innocent of collusion, it is not one the overall electorate will not buy into. It will be very much like Benghazi. Did Hillary make decisions that likely made a bad situation worse, yes, but, was she guilty of anything, no. So the public did not care.
However, the real funny thing about all of this is that the Dems and Pelosi are doubling down on obstruction, even after being walloped in the recent special elections. The Dems nationwide have become branded as the party of witch hunters, which certainly played a big roll in causing Ossoff to loose.
Even after a small, but notable, group of Dems called for Pelosi to step down and new leadership to take over (even Schumer is in the crosshairs), directly due to the recent losses and lack of any positive branding, I still see no evidence of anyone in a leadership position in the party trying to develop an actual message other then, "resist, resist, resist, obstruction, obstruction, obstruction, impeach, impeach, impeach!"
Now I certainly don't agree with Trump on everything, but one thing I have to is, "it would be a very, very sad day for Republicans" if Nancy Pelosi steps down.