if i were a liberal, i wouldn't necessarily be rooting for santorum, and i wouldn't cross over to vote for him in michigan. true, he looks like an easier opponent. but say he gets the nomination. there's always some chance that something goes wrong: a terribly mishandled international incident; a scandal; an economic crisis. then you end up living your liberal life in a santorum admin. now i wouldn't expect a santorum admin to be as much of a crazed disaster as it seems it could be; no one's going to be banning contraception. on the other hand, i think that, except rhetorically, you wouldn't practically be able to distinguish an obama from a romney admin at all, except perhaps in terms of military spending.