Parties are always "addled" and "divided," but sometimes a superior candidate can manage to impress the voters and prevail over the others. That hasn't happened this time -- certainly not yet.
"Philosophical coherence"? Sometimes that works. Sometimes you can find it. Reagan, I guess. But it was more Carter's lousy performance that mattered.
You could have a very philosophically coherent candidate and still lose. Goldwater's a good example. Purism in itself doesn't open the door to the White House.