Former Pennsylvania U.S. Sen. Rick Santorum responds to a question as he meets with reporters on April 14, 2014, at The Citadel in Charleston, S.C.

In South Carolina, Santorum Stays Out of Graham Race

Even conservative 2016 hopefuls seem wary of crossing Sen. Lindsey Graham.

Former Pennsylvania U.S. Sen. Rick Santorum responds to a question as he meets with reporters on April 14, 2014, at The Citadel in Charleston, S.C.

Rick Santorum speaks with reporters in Charleston, S.C. Santorum is the latest GOP presidential hopeful to visit the state but remain neutral when it comes to its U.S. Senate race.

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As eager as they are to drop into South Carolina, Republican White House hopefuls are just as inclined to stay out of the U.S. Senate race there.

[READ: Lindsey Graham Challenger Calls Senator 'Ambiguously Gay']

Former Pennsylvania Sen. Rick Santorum, speaking during a round of stops in Charleston Monday, was the latest to punt on the primary challenge to Sen. Lindsey Graham, R-S.C. 

The second-term Graham has attracted six primary challengers, but none has been able to marshal the resources or support to break out of the pack, easing the incumbent's chances of victory. A year ago, a robust right-flanking challenge to Graham – who has supported comprehensive immigration reform, a cap-and-trade measure and President Barack Obama's Supreme Court nominees – seemed likely.

The most financially solvent candidate, Det Bowers, recently tapped two Santorum hands to guide a late-breaking effort. Mike Biundo was Santorum's national campaign manager and Andrew Boucher was his political director, but Santorum – who weighed in during last spring's special election to fill Republican Sen. Tim Scott's old House seat – is steering clear of the fight for Graham's seat.

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He's just following the trend.

Sens. Rand Paul and Ted Cruz, both of whom have frequented the Palmetto State over the last year, have also declined to choose sides, saying they are staying out of primaries with incumbents.

That's a blessing for Graham, but also shows that the candidates-in-the-making see little reward in antagonizing the state's senior senator if he's likely to win re-election.

Graham isn't completely out of the woods – the primary isn't until June 10 – but if candidates were going to hop on an insurgent's wagon, it would have happened by now.