Can Annie Andrews Unseat Graham? Republican SC Senate Odds Fall to 78%
Graham pulled just 49% in his own primary. A Siena poll now shows Andrews leading 50-43, triggering an 8pp market drop in three days.
Bottom line
Graham pulled just 49% in his own primary. A Siena poll now shows Andrews leading 50-43, triggering an 8pp market drop in three days.
- Market average
- 86% YES
- Best listed price
- 86¢ · Polymarket
Trade YES at 86¢Siena Poll Rattles South Carolina: Lindsey Graham Trails Democratic Challenger Annie Andrews
Lindsey Graham has held his South Carolina Senate seat since 2003. He survived a bruising 2020 challenge from Jaime Harrison, who raised over $100 million and still lost by 10 points. South Carolina hasn't elected a Democratic senator since Fritz Hollings won his final term in 1998. Donald Trump carried the state by 13 points in 2024.
Against that backdrop, a Siena College poll released July 1 changed the calculus: Annie Andrews, a pediatrician and former congressional candidate, leads Graham 50% to 43% among 601 likely voters. The margin of error is ±5%, which means Andrews' lead is within the bounds of statistical noise. But the direction of the result, not just its magnitude, is what rattled both parties and the traders watching prediction markets.
Graham already showed vulnerability in the June 9 Republican primary, where he secured the nomination with just 49% of the vote against a field of relatively unknown challengers. Mark Lynch pulled 29%, and the remaining candidates combined for 22%. For a four-term incumbent in a deep-red state, failing to crack 50% in a primary is a warning sign, not a victory lap.
The poll is the spark. But markets were already pricing South Carolina as nearly certain Republican territory, which is why the repricing has been so sharp and so fast.
Republican Party's South Carolina Senate Odds Fall 8 Points in Three Days
On both Kalshi and Polymarket, the Republican Party's implied probability of winning the South Carolina Senate seat has dropped from 86% to 78% in just three days. That 8-percentage-point decline is extraordinary for a race that, until this week, most analysts classified as "Safe R." For context, an 8pp move on a seat with this partisan lean is the kind of repricing you'd normally associate with a candidate dropping out or a major scandal breaking.
The move is not uniform across platforms. Kalshi prices the Republican Party at 74%, while Polymarket holds at 81%. That 7-point spread between the two platforms suggests active disagreement among traders about how much weight to assign the Siena poll. Kalshi's lower price implies that its trader base is taking the poll more seriously, or at least hedging more aggressively against a Graham loss. Polymarket's higher figure suggests more confidence that structural Republican advantages in South Carolina will reassert themselves.
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Either way, the speed of the move is the story. Markets don't reprice "safe" seats by 8 points because of one poll unless that poll confirms a pre-existing suspicion. Graham's underwhelming primary performance and broader GOP anxieties about the Senate map created the kindling. The Siena number lit the match.
Why Annie Andrews Could Actually Beat Lindsey Graham in South Carolina
Take the strongest version of the case against the Republican Party here. It requires three conditions to hold simultaneously, and none of them is implausible.
First, Graham's in-state favorability has eroded. His primary performance is the clearest evidence. Incumbents who draw less than 50% in primaries are historically vulnerable in generals. Graham's positioning as alternately a Trump ally and a bipartisan dealmaker has left him without a firm base among either populist Republicans or moderate suburbanites. He has managed to irritate both flanks without fully securing either.
Second, Andrews fits a profile that has worked before. She's a pediatrician, a profession that consistently ranks among the most trusted in Gallup surveys, and she can run on healthcare access in a state where rural hospital closures have become a genuine crisis. Her previous congressional campaign gave her infrastructure and name recognition in the Charleston media market, which covers a growing share of the state's population. South Carolina's demographic shift, driven by transplants from blue-leaning metros settling in the Lowcountry and Upstate suburbs, is slow but real.
Third, midterm environments matter. If the national political environment is hostile to the party controlling the White House, even deep-red states can produce upset-caliber margins. The 2017 Alabama special election, where Doug Jones defeated Roy Moore, proved that exceptional circumstances can flip even the reddest seats.
The Siena poll's ±5% margin of error means a true tie is within the confidence interval. But so is a Graham lead of up to 2 points. The honest read: this race is more competitive than anyone expected six months ago, and the market's 22% implied probability for a Democratic win is pricing in genuine uncertainty, not panic.
Why Graham and Republicans Are Still Heavy Favorites to Hold South Carolina
A 78% implied probability means the market expects the Republican Party to win this seat roughly four out of five times if you could replay the election repeatedly. That's a meaningful favorite, and the structural reasons behind it are formidable.
South Carolina's partisan voter index leans Republican by roughly 8 to 10 points, depending on the cycle. Even in 2020, when Harrison spent record-breaking sums and national Democrats poured resources into the state, Graham won by a comfortable margin. The state's electorate is older, whiter, and more conservative than the national median, and midterm electorates tend to amplify those characteristics rather than dilute them.
Money is another factor. Graham has consistently ranked among the Senate's top fundraisers across multiple cycles, and the general election field includes multiple minor-party candidates who could siphon protest votes that might otherwise consolidate behind Andrews. The presence of a Constitution Party candidate (Mark Hackett), a Libertarian (Kasie Whitener), and three independents fragments the anti-Graham vote in ways that typically benefit the incumbent.
One Siena poll does not erase decades of electoral history. But it does explain why the market repriced from 86% to 78% rather than holding firm. The correct read on this market: South Carolina is not yet a toss-up, but it is no longer a foregone conclusion. Republican Party shares at 78% are pricing in a race that could tighten further if subsequent polls confirm the Siena finding, or snap back toward 85%+ if the next round of data shows Graham with a conventional lead. The November 3 resolution date leaves four months of volatility ahead. Traders buying Republican Party contracts at 74% on Kalshi are getting a better price than those paying 81% on Polymarket for the same outcome, and that spread itself tells you the market hasn't reached consensus on what this race actually is.
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The story so far: South Carolina Senate winner?
7 updates · Apr 11 – Sep 27
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