Fox News is doing a series called 12 in 12. They are interviewing "candidates" for the upcoming presidential election. Mitt Romney declined to interviewed. So far they have done two so-called favorites.
Mitch Daniels did amazing things as Governor. He reduced the spending, and he reformed the state employees health care with market based solutions. He doesn't seem to want to run, even though his name keeps coming up. Another downside is that he did work for the Bush administration, which isn't exactly the best resume enhancer.
Haley Barbour did an amazing job during Katrina. His job was proof that New Orleans was much more complicated than the Bush bashing that went on during the crisis. He just did the job and asked for the federal help right away, instead of having meetings about asking for help. The down side with him is that he was a lobbyist for a while, that will work against him. But his views on taxes and spending are solid, especially when you consider that Mississippi is a very poor state.