Jamelle Bouie
Over at his blog, Jonathan Bernstein makes an important point about Mitt Romney's place among the GOP field:
Indeed, as far as I can tell there's virtually no separation between Romney and the other candidates on core conservative issues. The main "problem" with Romney from their point of view is not his current professed positions; it's whether he can be trusted, given his record in Massachusetts (including both his time as governor and his two campaigns).
For all of the talk about Romney being a moderate, when you compare him to his rivals for the nomination, he's a doctrinaire conservative on everything from reproductive rights (he doesn't like them) to taxes (they should be lower, especially for rich people). Some people hope that Romney's moderate side will emerge should he become president, but that ignores the political circumstances that shape the incentives for incumbent politicians.
Because of his record in Massachusetts, Romney will always face suspicion from the conservative base, and as a result, he's most likely to err on the side of conservatism. At any point during his presidency, when given the choice between a conservative option and a moderate one, he'll likely choose the conservative one. Of course, some of this depends on the exact issues that emerge on his watch and the composition of Congress. In a world where Romney has the White House but Democrats have a chamber of Congress, he's more likely to compromise. But barring that, it's unwise to assume that Romney will become more reasonable in office. He has campaigned as a Tea Party conservative, and in all likelihood, he'll govern as one too.