South Carolina's entrenched Republican lean and absence of a Democratic Senate victory since 1998 anchor trader expectations for Darline Graham despite recent polling tightness. Appointed after her brother Lindsey Graham's July death, she secured the GOP nomination and benefits from Trump rallies plus party infrastructure in a state he carried by double digits in 2024. Annie Andrews, a pediatrician emphasizing pocketbook issues and moderate stances on healthcare and immigration, has narrowed the gap by attracting independents and some Republican crossover in NYT/Siena and Citadel surveys showing near ties or single-digit margins. Graham's incumbency advantage and structural base rates nevertheless sustain her lead in implied probabilities ahead of the November 3 election.