It's unlikely but some have speculated that former presidential candidate Gov. Mitt Romney may be considered. His Massachusetts healthcare plan -- which requires citizens to purchase insurance -- was criticized by conservatives during the 2008 election, but emulates what Obama wants to implement nationally.
If Obama were to entertain this unlikely scenario (a Republican in charge of healthcare?!), Marc Ambinder notes he would definitely need an active pro-choicer to lead in another role in order to appease the base. Romney is a pro-life Mormon whose nomination would like enrage liberals either way, though.
Fifty-six percent of people in this survey said Romney would not be a good fit and the folks over at Mitt's place said "Interesting, but it’s not going to happen." I agree. Even if it was possible, it would rob Romney of support amongst the conservative base, thwarting his chances at another presidential run. He was criticized for his healthcare plan last year and a position like this may only force a round of flip flops later.