Perhaps. The Convention is two eons and the general election is another eon further. This has been the year of suprises. But, it should be no suprise that the glow of Obama will dim.
See that answer Anyone But McCain shows to me that people would rather throw away an election for President to the other party than accept there are variations within the Republican Party.
You cannot accept that one large group of people are going to agree on all concepts - however for one to cross party lines at this point and hope the other side will win the presidency is a shocker to me.
Might even be best for the Republic Party if they left.