USA Today writes on a not-well-known rule that might prevent any interesting potential surprises at the Republican National Convention when it comes to any candidate who isn't Romney or Santorum:

There's been lots of talk in the last couple of days about a GOP rule that states a candidate has to have a plurality of delegates from at least five states to get on the ballot at the convention this August.

Gingrich has only won two states—South Carolina and Georgia—so far in the GOP race and lags well behind front-runner Mitt Romney and Rick Santorum in delegates.

The rule would also seem to apply to Ron Paul, who has yet to win a state or primary and has the fewest convention delegates based on a tally by the Associated Press.

Here's what Rule No. 40, Section B states in the Republican National Committee rulebook:

Each candidate for nomination for President of the United States and Vice President of the United States shall demonstrate the support of a plurality of the delegates from each of five (5) or more states, severally, prior to the presentation of the name of the candidate for nomination.

Reince Priebus, chairman of the Republican National Committee, told NBC News that the rule is an important one.

"So when these candidates are adding up their delegates or when people out there have a particular issue that they would like to move at the convention, they had better make sure they at least have a plurality of five states to make these things happen," Priebus said.

Randy Evans, a Gingrich adviser, said Gingrich could still get a plurality of delegates, through a combination of wins in upcoming contests such as one in the District of Columbia, and by peeling off delegates who aren't bound by the results of primaries or caucuses.