My opinion is that Gingrich and Santorum represent different factions of the conservative vote, and that the overlap is much less than most FR observers think. A Gingrich droput would probably send more voters to Romney or Paul than to Santorum.
Gingrich is pro-life and pro-2nd Amendment. The only difference I can tell is that certain folks think Gingrich is pig for committing adultery, which they cannot forgive, and ignore some of the crapola Santorum had done that is NOT pro-life!
Go figure! I believe the MSM has had a huge impact on this election. The liberals/progressives fear, really truly fear Gingrich, so he is getting more negative exposure by the Meida than Santorum ever will receive.