South Carolina Senate Special 2026

South Carolina holds a special Republican primary on August 11 for the US Senate seat left vacant by Lindsey Graham's death in July. Governor McMaster appointed Graham's sister, Darline Graham, to hold the seat through year-end; she now runs for the full term with President Trump's endorsement and leads the Kalshi book at roughly 70%, ahead of Representatives Ralph Norman and Russell Fry. This workspace tracks the primary distribution across Kalshi and Manifold, spotlights the two candidates the market still has in play, and pairs the November general-election books so the near-term primary sits inside the full race. A runoff, if no candidate clears the threshold, follows on August 25.

Kalshi and Polymarket both price the November 3 general election independent of who wins the primary. In deep-red South Carolina the Republican nominee is heavily favored, so these books move less than the primary on any given day—watch them reprice if an unexpected name takes the nomination.

• Darline Graham vs. the field. The appointee leads near 70% with Trump's endorsement; the cleanest read on an upset is whether Ralph Norman's leg climbs off the mid-20s.
• Cross-exchange spread on the primary. Kalshi carries the depth (~$132k/24h); Manifold's thinner book is directional color—sustained divergence is usually liquidity, not disagreement.
• Runoff risk. With ten-plus names filed, no candidate clearing the majority sends the top two to an August 25 runoff. A compressing front-runner leg is the tell.
• Primary to general. The Kalshi and Polymarket seat-winner books price the November race; if the nominee changes, expect them to reprice sharply rather than gradually.