It's important to remember than John's politcal hero is Teddy "Moose Party" Roosevelt.
If John runs for POTUS, he will either run as an Independent (the straight talk express) or find a suitable venue wherein he can proclaim in an act of glorified statesmanship that "the GOP has left him, and that he feels the democrat party now best represents his views," and they will welcome him with an open DNC checkbook and Hillary will be his VP running mate. John is old and she can almost be guaranteed the presidency by his death or his promise to not seek a second term.
There you have it, so says I, onyx. :)
Hillary! spent 8 years in the White House as second banana already. If that memory doesn't stick with you, it certainly is seared into the consciousnesses of her core supporters.
They won't tolerate Hillary! running for a position which requires a microsecond more of the WH second-banana position.
It's more than political to them, it's assuredly personal.
They also consciously recognize McCain for what he is, a political turncoat opportunist with no core belief system.
If McCain can betray the Republicans so frequently and so publicly, what could ever be perceived as restraining him from betraying his "friends" on the other side of the aisle later on, as President-- or reneging on any presidential campaign pre-nup agreement with Hillary!, for that matter?
Besides, he is a white male, which is to say, he is considered equivalent to subhuman among Hillary!s core supporters-- no matter what he professes to support or not support politically at any given time.
I wouldnt think that anybody that valued their life would want their heartbeat to be between Hillary and the Oval Office. I sure wouldn't.