The only way I can see Lindsey Graham losing in a SC Republican primary is if you run Trey Gowdy against him. He's not going anywhere. These other challengers are pulling in single digits according to a new Winthrop Poll
Lindsey Graham also getting 1/3 of those who support the tea party. He's not in any trouble in SC. Yes he's under 50% but 35% of voters are still undecided.
I guess one thing to remember about Republican primary elections is that there is a big difference when trying to knock-off an incumbent (at least this time around). In SC and in KY, challengers are getting trounced. Matt Bevin, after a year on the scene is getting less than 20% against McConnell. In SC, the tea party candidate is pulling 8%.
When Ted Cruz and Rand Paul won Republican primary elections, it was for open seats, not against incumbents. Rand Paul defeated Trey Grayson in KY for the open seat left by the retiring Sen. Jim Bunning. Ted Cruz defeated David Dewhurst in Texas for the open seat left by the retiring Sen. Kay Bailey Hutchison.
Here are the SC Republican primary numbers from Winthrop