Now that we have a presumptive candidate in Romney, it's worth noting what an interesting choice this is. Romney is the quintessential politician. He doesn't stick to his guns, but fashions his message based on who he's talking to. He is consistent only in his inconsistency.
The funny thing about Romney is that he is a pretty poor choice to go up against Obama. Why? Because with Romney, conservatives won't be able to use their most damning evidence of Obama failure: health care. Also, any mention of Obama being a closet Muslim would be seen as hypocritical, since members of the GOP have already complained that the Obama administration may, sometime in the future, attack Romney for being a Mormon.
Then, you've got the die-hard conservatives out there who simply don't like Romney. It used to be that a political party would be able to encourage its fringe to rally around the inevitable candidate. However, many in the super-conservative base have said that they will simply not vote if it comes down to a choice between Romney and Obama. Even Santorum, who most closely represents that demographic in terms of values, has said that Obama would be a better choice than Romney. The logic of this statement escapes me (and Santorum as well), but it's a telling statement. Some in the conservative base would rather wait four more years when they have a better shot at the White House than stain their reputations now.
Romney is going to have a fight ahead of him, and it's probably going to be more difficult than he realizes. Not only is he going to have to fight Obama's engaged and committed fans, he's also going to have to play a delicate balancing game between moderates and ultra-conservatives, both of whom he will need in order to win. He's going to have to explain why he supports the middle class but not the health care reform that helps them. He's going to have to justify spending at the federal level while simultaneously decrying public spending. I think it will be difficult for him.