Mitt Romney shouldn't have more than a snowball's chance in hell of getting nominated president for the Republican party in this 2008. Furthermore, I don't agree with the fiscal right turn of the Republicans, a balanced budget and an end to elitist/corporate socialism is what people wanted IOTL Tea Party movement along with less government in general, but I do agree that Republicans would be drawn to Romney (as they were in 2012) because he was a businessman. The fact that he was a predatory venture capitalist that lied to their faces about where he stood on just about every issue wasn't taken seriously in those days for whatever reason.
Obviously that died when the establishment effectively infiltrated and neutered the Tea Party movement and claimed it for it's own use and rendered the term "Tea Party Republican" meaningless.
Meanwhile, Huckabee should have much more of a shot at winning in this ATL 2008 than he did OTL. For one, he can get in on the ground floor of the Tea Party movement more effectively than just about anyone else save George Allen, for another Huckabee has always been in the mold of a traditional southern governor. In this 2008 that's a good thing because he can tap into that well of populist charm and policy that any good southern governor has in spades.
The less said about McCain's chances to win, the better. lol