If there had been a 269/269 tie

[tpfkaw]

Minnesota was a 4-4 split though, I believe. My guess is that either someone would give in and break the tie (Romney would have well over 25 by that point so it wouldn't even matter), or it might even end with a stalemate and no vote being given. I'm shaky about the latter though.

Collin Peterson might've broken party lines if it wouldn't effect the outcome and he had permission from leadership.

[tpfkaw]

I think it would look highly improper for the Senate to appoint an opposite-party VP, since it would in effect be an open invitation to assassinate the POTUS.  I suspect you'd either have Ryan being appointed with Democrats voting for him or abstaining, or maybe, if Romney loses the popular vote and Democrats are particularly bitter, a compromise candidate acceptable to both sides (perhaps Colin Powell, Joe Lieberman, Dick Lugar etc.).