The conventional wisdom (which, of course, changes by the minute given this election), is that a vote for Santorum is a vote for Romney, that Santorum can’t win, but he can take enough of the conservative votes, who would otherwise vote for Gingrich, to give Romney the plurality win in Florida and elsewhere.

The polling showing Gingrich’s surge and victory suggest otherwise.

Gingrich has surged primarily by taking votes from Romney, not be taking them from Santorum.  At the end of last week, both Gingrich and Santorum picked up considerable support all while Romney was dropping.   Note how Newt and Rick finished seven and five points ahead of their respective final polling averages.

http://www.realclearpolitics.com/epolls/2012/president/sc/south_carolina_republican_presidential_primary-1590.html.

In Florida, Gingrich’s surge has been primarily a story of Romney losing support.  Comparing Rasmussen’s polls taken the day after NH with the day after the SC primary, we see the following:

Gingrich has picked up 22(!) points.  Romney has lost 9 points.  Santorum has dropped 4 points (going from 15% to 11%).

If Santorum revives some, as I think he will with the next two debates (as he clearly did after Thursday’s), it is far from clear that his gain will be at Gingrich’s expense.   The SC numbers suggest that he gained in the final days at Romney (and Paul’s) expense.

Indeed, if Romney has a week like last one’s, we may very well see his support plummet, with Santorum and Gingrich as the two strongest candidates….until a few weeks from now.