At first glance, when gaming out Graham’s chances of surviving a multi-candidate primary and going on to win re-election, the logic seems simple: the more competitors, the merrier.

For a lawmaker who has long raised the ire of some rank-and-file conservatives with his deal-brokering and occasional breeches from Republican orthodoxy, there is a benefit to splitting the Tea Party vote into as many parts as possible.

But this line of reasoning has a potential flaw: South Carolina electoral law stipulates that a candidate must win at least 50 percent of the primary vote to avoid a runoff, and Graham’s chances of reaching that threshold could become even more difficult with additional names on the ballot.

And in a one-on-one runoff , all bets are off for Graham, who would likely have to fight tooth and nail for his political survival.

Former South Carolina GOP Chairman Katon Dawson — who runs a super PAC supporting the already well-funded incumbent — explained in stark terms the challenge ahead: “Fifty percent in a three- or four-person race is a hard number to get to. It just is. My expectation would be a runoff.”