Although this was a good tweet I would have written is as " IF the WP story is true, I am being investigated for Firing Comey by the person who told me to Fire him"  He probably isn't actually being investigated seriously for Obstruction as the Constitution gives him the right to fire the FBI director for any reason at all.  With Clinton, Obstruction involved lying under oath and witness tampering which is not allowed and even still only the Congress voted to impeach him, not the Senate as the public was NOT on side with removing Bill for obstruction when the underlying crime in that specific case was a blow job. ( They couldn't get  him on the illegal whitewater deal) Firing the FBI director is ALWAYS permitted and does not cause any investigations to end.