Mueller is like Comey & has already planned on the scenario of getting fired by Trump.  If Mueller gets fired, like Comey he will release his poison pill & whatever damning evidence he has against Trump will get released to the public and Congress.  Congress, including many Republicans, in response to  their constituents, will have continue to investigate Trump & critical mass would be acheived to start impeachment proceedings.  Even if Trump does not get impeached, he and his adminstration will be completely paralyzed and disgraced.  There is no way he will ever get Republican support for re-election in 2020.  If this occurs before the 2018 Congressional elections, Democrats can take back Congress if they run on the platform of putting Democrats back in charge of Congress to get rid of an unstable out of control tyrant. It is over for Trump.  The US constitution & our principles of democracy will prevail and one way or another will remove a wannabe crooked, dictator president.