Lindsey Graham, the incumbent Republican senator from South Carolina , leads a primary that could force his first runoff since 2002 if he fails to clear the 50% threshold. A recent Citadel poll shows him at 46% against challenger Mark Lynch’s 36%, while 18% of likely GOP voters remain on the fence.

Graham at 46% vs Lynch 36% in Citadel poll

The Citadel’s latest survey of likely Republican primary voters places Graham ahead but well short of the majority needed to avoid a second round. According to the poll, Graham’s support sits at 46% while Lynch trails at 36%, leaving a margin that could evaporate if undecided voters swing the other way.

Graham’s campaign has leaned on his long record of avoiding runoffs, citing a 2020 primary win with over 67% of the vote. However, the current numbers suggest a much tighter race, and the 18% of undecided voters could be decisive.

18% of GOP primary voters undecided, raising runoff risk

The same Citadel poll highlights that 18% of Republican primary voters have not yet chosen a candidate. This sizable bloc is large enough to push Graham below the 50% mark,triggering a runoff scheduled for June 23.

If no caandidate reaches the majority, South Carolina law mandates a second‑round election, a scenario Graham has not faced since his first Senate victory in 2002.

Trump backs Graham despite Iran war stance

Former President Donald Trump has publicly endorsed Graham, urging voters to stick with the incumbent. Trump’s statement that the United States will achieve “total victory” in the Iran conflict adds a layer of complexity, as Graham’s hawkish position diverges from the isolationist wing of the GOP.

Graham has urged constituents to “send their sons and daughters to the Mideast,” framing the war as a necessary sacrifice to prevent Tehran from acquiring nuclear weapons. This rhetoric has drawn criticism from Lynch’s camp, which accuses Graham of abandoning the “America First” principles championed by Trump.

Lynch courts Trump‑aligned voters with hard‑line America First message

Mark Lynch, a businessman, has positioned himself as the true Trump‑aligned candidate, securing endorsements from former National Counterterrorism Center Director Joe Kent and ex‑Border Patrol commander Gregory Bovino. His campaign emphasizes a hard‑line “America First” approach and paints Graham’s Iran stance as a betrayal of nationalist values.

Lynch’s messaging resonates with the party’s isolationist faction , which views the ongoing U.S. involvement in Iran as an unnecessary foreign entanglement that could hurt the economy .

Will Graham break his no‑runoff streak?

The key unanswered question is whether Graham can convert enough undecided voters to maintain his historic avoidance of runoffs. The poll does not reveal where the 18% undecided bloc leans, nor does it capture late‑breaking endorsements or campaign developments that could shift the balance.

Additionally, the impact of Graham’s Iran rhetoric on moderate Republicans remains unclear, as does the potential effect of any new statements from Trump in the final days before the primary.