As long as the Presient, any President, stays within the lines as drawn by the Constitution, he cannot be indicted.

It is a fact that Trump had good reasons for firing Comay,  reasons outlined by the Assistant Attorney General.  Mueller was rejected from being head of the FBI and the following day,  was appointed as the Special Prosecutor   . . . .   so "yes" there was a conflict of interest rooted in possible bias.  The President had the right to fire Mueller.  Had Mueller been fired,  the Russian Hoax would have continued unimpeded.    Guilty people use bleashbit on their hard-drives,  hide their emails by the tens of thousands,  destroy the Sim Cards in their  collection of Blackberry phones,   and use hammers to destroy their phones.  Trump did none of that,  even refusing to hide behind "executive privilege.    In fact,  he complied with all the demands of Mueller.  "What about his refusal to be physically interviewed?"  And the answer to this is rather simple.  After a year of negotiations,  Mueller decided he did not need to question the President and allowed the President to continue without an interview   . . . . .   hence,  "no obstruction."
 

“And the best precedent for that is George H.W. Bush, who pardoned Casper Weinberger and five other people on the eve of the trial,” Dershowitz said. “The special prosecutor said he obstructed justice, but he couldn’t be charged with it. And they never mentioned the Bush case in the Mueller report. Mueller was in the Bush administration. Barr was in the Bush administration. And they deliberately omit as the leading precedent, which would preclude a president from being charged with obstruction for simply exercising his constitutional authority.”  ~  Allen Dershowitz