First, any candidate who gains the nomination will find that he or she has all the resources necessary to fight the battle against Obama.
Second, once a candidate is nominated after the primary season they gain the WHOLE support of the Party (save for dissidents who toss their votes aside).
Third, we can "pre-select" a candidate now before the primary season really even gets under way (Romney) or we can watch and wait to see what happens as the primaries gain steam.
Fourth, watch Santorum... He actually seems to have won Ohio after the certification and that will give him a bump. No one was going to win in New Hampshire except Romney -- that was a given -- it is his back yard and the moderates there would select none other, but the distaste for him elsewhere will be telling. They refused him 4 years ago and will again GIVEN A TRUE CHOICE (of which Paul is not). In a sense, Santorum is akin to introducing Palin after the Convention, only he actually gets some time to run first, and he does not come with some of the baggage that Palin brought to the table. As soon as voters actually realize his true conservatism his stock should rise (and once he gains a few PACs that will help as well).
Fifth, we have to get beyond the national media chosing the candidate for us. Romney's meme, supported FULLY by the national media is that "he is the destined candidate." Hogwash!