He just really isn't that conserative and that will show once the debates starts. Singing Obama's praise right before the 2012 election certainly didn't help him but what will kill him is that he is seen as being weak on gin control. Love them or them there is significant percentage of republicans who will refuse to support a candidate they see as weak on guns.
I would be happy to be proven wrong but I don't think can win the republcian nomination in any but the bluest states and be wishy washy on gun comtrol.