Nonsense. The Constitution states that the winner must have a majority of the electoral votes cast. If McCain doesn't then in your scenario regardless of what happens to Obama the election would have to go to the House.
Your “expectation” may not be what the electors would do. They are free to anything they want.
But these are Democratic electors. They'll go for Biden before McCain.
Electors would not be cast for a unqualified candidate or accepted by the EC.
The constitution refers to a “majority of the electoral votes appointed...” and they are appointed by the States. So the decision first rests with the States. These are sent to the President of the Senate who opens them in front of the whole Congress. Now I would not assume that should Zero be disqualified that would mean the states would all just give them to Biden. Should they do so that opens up a whole can of worms wrt how to select a VP.
Electors are not “Democrat” or “Republican” they are completely free agents. How they would react to such a constitutional crisis as this would be is totally unpredictable.
I do agree this would end in the House should it transpire.