I guarantee the number one complaint from the Right if Romney loses to Obama will be that he wasn't conservative enough,
and then, when you ask them which 'conservative' candidate could have beaten Obama,
they'll mumble something incoherent, and wander off.
Daniels. Jeb Bush. Mike Huckabee. Any of them would have probably done fine.
I think Romney's lack of genuine conservatism is part of the problem. So are
1) His goofy religion
2) His slimy business practices
3) His tendancy to say really stupid things like "I like to be able to fire people"
But what is going to save Obama is that last time, 69 million people voted for him. 69 million people who aren't ready to admit they made a mistake, because really, admitting a mistake is against human nature. Rationalizing mistakes is human nature. So what we will see with those people is finding some way to rationalize what they did in 2008 while doing it again in 2012.
This is why incumbents almost always win second terms, unless there is something like a third party insurgency undermining his base (Anderson in 1980, Ross Perot in 1992.) people will stick by their bad decision.
Meanwhile, Romney has to win over all the people who voted for McCain last time all over again, and THEN try to get some of the folks who voted for Obama to either stay home or vote for him. It's a Herculean labor, when you come to think of it.
And the fact that Romney isn't at all likable or someone most people can relate to doesn't help matters in the least.