The electors have to cast their ballots first. If they find out that O is not eligible, most will cast their ballots fro some other Dim, for President. That could be Biden, but it could be someone else just as well.
After they cast their votes, and the tally sheets are sent to the President of the Senate (the current VP, the eviil Dick Cheney) is as early as the House and Senate could get involved. But they must pick from the top 3 electoral vote getters, who can qualify, which leaves McCain for President.
Cool. Thx for the clarification.