Just consider for a moment just how low the bar is set. We have discovered that neither adultery (Gingrich and allegedly Cain) nor serial sexual harassment (again, allegedly Cain) is a disqualification by itself, it takes both to force a candidate out of the race. This is an electorate that cheers when a candidate boasts of the number of people he has executed. Santorum has said plenty of really stupid stuff and even more really incredibly stupid stuff ,but I haven't heard any Republican repudiating any of it. We won't even discuss his regressively idiotic deficit tax plan, but you can read about it here!
Santorum is a hate-monger. But Gingrich and Paul have both pandered to the same prejudices. Mitt Romney spends so much time pandering that no one, even his staff doesn't know where he stands day to day on any issue.
None of the commentators I have read think that Santorum is likely to beat Obama. But at this point Romney does not look a lot better. Republicans don't seem to think any better of him than Democrats.
Santorum would deliver social conservatives to the polls in November. Santorum knows how to pander and flip flop as well as well as Romney. He's even learning how to do the patented Gingrich, "I know what you think you heard me say, but that's not what I said" trick. He would not be as a catastrophic nominee as Paul or Gingrich would be. That might be enough for the GOP to pick him. If the establishment can't get their candidate of choice, Santorum is the least worst alternative. This may be the reason that George Will and Rupert Murdoch have been talking him up. This could get really messy, fast.