Despite the respective calls by the Gingrich and Santorum camps for the other to get out of the race so the two can stop splitting the anti-Romney vote, there have been only two states that Romney won where the combined vote of the two would have been decisive—Michigan and Ohio—and in both of those state it would have shifted only a few delegates.

In what are expected to be tight three-way contests in Mississippi and Alabama today, Santorum and Romney are neck-and-neck. But even if Gingrich were to exit, the two would still be neck-and-neck. A poll conducted this weekend by Public Policy Polling (PDF) shows Romney leading Santorum by 1 percentage point. When the same respondents were asked who they would support if Gingrich were not a candidate, the results hardly change: Santorum takes a 3-point lead—still within the poll’s margin of error…

While polling numbers suggest Romney’s margin would tighten somewhat in a one-on-one race against Gingrich or Santorum, looking backward even if Santorum and Gingrich’s votes had been combined, it would have swung just a handful of delegates, and not a single winner-take-all state.