Let's play the political chess game out two or three moves.
Suppose the anti-Trump forces bring him down, do the nominal Trump supporters have any choice other than to stop shielding Obama ($$$ to Iran) or the Clintons (plural)? It becomes a matter of saving face.
That seems to be the current rule-set: Never go down alone. The old rule-set was tit-for-tat.
Truth be told, I would be OK with Pence as POTUS if it meant that Obama and the Clintons were held accountable.