I wish I had the means to get every senator and House representative to answer this question anonymously:
If you were granted the power to personally appoint the next President, but it had to be a member of the party opposing your own, whom would you pick?
I wonder how many would pick the person they thought would be best for the country; whether some would pick someone they hoped would fail, but not so catastrophically as to destroy the country -- and what in fact those choices even mean. Someone of sincere ideological conviction would have to hope that his or her pick "failed" in some senses, i.e. in getting preferred policies enacted, while succeeding in others, perhaps mainly on the foreign policy front.
Though I'm not in Congress, I have a preferred Republican, but my choice is a kind of cheat: Michael Bloomberg, a genuine RINO. Beyond that, I'm kind of clueless. Huntsman seems able and sane, but I honestly probably just vacuumed that impression up from Fallows. Bush Sr., I guess, is a little old for the job.
P.S. I wonder how many Republicans would choose Barack Obama.