Graham would be a heavy favorite to win a third term in November. Watch a debate between Graham and his challengers.
Falling shy of a majority today, Graham could join Mississippi Sen. Thad Cochran in facing a runoff before securing nomination for reelection.
There are primaries in five states, led by South Carolina and Virginia, today.
In Virginia, House Majority Leader Eric Cantor is looking to clear his first hurdle in his quest to secure an eighth term in the 7th District in and around Richmond. The House’s second-ranking Republican is opposed in the primary by Dave Brat, a college economics professor who’s aligned with the limited-government agenda of Tea Party activists.
Like House Speaker John Boehner, who took 71 percent of the vote in an Ohio Republican primary in March, Cantor is expected to win renomination handily, though he may receive a smaller share of the vote than Boehner.
Farther north, in Democratic suburbs just outside Washington, seven Democrats are vying to succeed retiring Democratic Rep. Jim Moran in the 8th District. The 10-candidate ballot includes the names of three candidates who have withdrawn.
The best-funded and best-known Democratic candidate is Don Beyer, a former lieutenant governor who led fundraising efforts for Howard Dean’s 2004 presidential campaign and served as ambassador to Switzerland.
The winner of the Democratic primary surely will win in November in a district that gives about two-thirds of its votes to Democratic candidates running statewide.
Maine, Nevada and North Dakota also are holding primaries today.