Romney/Daniels, if not Daniels, Thune
Daniels/Thune
If Romney wins the GOP nomination, he'll need to choose somebody who can solidify economic and social conservatives dissatisfied with Romney. Also, Romney needs to choose a VEEP candidate who can appeal to tea partiers. Daniels, who called for a truce on social issues and called for a possible VAT, would not qualify (though I like Daniels). Thune, who voted for TARP, would not qualify as an economic conservative in the minds of tea partiers. IIRC, John Thune refused to strip Lisa Murkowski of her seniority on the energy committee, which pissed off a lot of tea partiers.
Bobby Jindal IMO would be a great VEEP candidate for Romney. He is a solid economic and social conservative, who can reach out to economic and social conservatives also squeamish about Romney.
If Romney wins the GOP nod, I think Romney/Jindal would be a really strong ticket (though Romney isn't my first choice for the GOP nod).