Can be summed up in two simple points. Oh, there's more problems with him that just these two points, but if you want to boil everything down, these two points are it:
1) RomneyCare, or as Pawlenty put it so well before he refused to fight, "ObamneyCare". Romney refuses to admit that RomneyCare is a bad idea. He refuses to admit that socialized medicine is a bad idea. And if he won't do that, then we don't need him in the Oval Office. What happens if we finally get the votes to repeal Obamacare, and President Romney vetos the repeal?
2) He won't fight. He's trying to be Mr. Nice Guy. Remember what happened to the last Mr. Nice Guy? We're not just fighting Obama, we're fighting the Media, who is desperate to keep their God-King enthroned. If you're not going to fight, and if you're too fucking stupid to see that the Media is going to throw everything they have against you, then you will. Not. Win. It's that simple.
Is Gingrich the ideal candidate? Hell no. But at least he swings at the Media when they take shots at him, and he's put more than a few of the pompous fucking jackasses in their place, which is more than Romney can say. If Romney isn't willing to fight both the media and Obama, he's going to lose.
And you know it.