the far-right wing of the GOP have too many candidates to choose from (bachmann, perry, gingrich, santorum, cain at one point) and, when you throw in libertarian ron paul, that splits the anti-romney vote too many ways. if there was one far-right candidate, they would have had a better chance. romney's goal is to keep them all in the race for as long as possible because as all these candidates linger on, romney's establishment GOP superPAC backers collect more money and will systematically crush every new "surging" opponent.
i suspect the GOP elders are pushing for romney as the least-worst/vaguely plausible/least embarrassing candidate for 2012, but have no real expectation of beating obama. that's why all the strongest GOP candidates -- mitch daniels, chris christie, jeb bush (!), etc. -- bowed out this year. they've given up on 2012 and all have their sites set on 2016.