Without a doubt, the Huckster too played a big role in giving the nomination to McCain. By splitting the so-con 'abortion is the only issue, period' vote between himself and Romney, the RINO squishes and 'Rat crossovers got their man.
Rudy got New Jersey and New York to switch to winner-take-all. When Rudy fell in Florida, McCain subsequently won both of those states, and IMO at that point he was just too far ahead for anyone to catch him.