South Dakota’s at-large House seat remains a strongly Republican-leaning district following the open-seat contest created by Dusty Johnson’s gubernatorial bid. Republican nominee Marty Jackley, the state attorney general, secured his party’s nomination by a wide margin in the June primary, while Democrat Nicole Gronli advanced unopposed. Trader pricing on victory margins clusters between 15 and 25 points for the Republican, reflecting the state’s consistent partisan baseline and limited recent polling that shows only modest narrowing from historical levels. With the November 3 general election three weeks away, the absence of major late-cycle developments, campaign finance shifts, or national headwinds has kept implied probabilities stable, though any unexpected turnout surge among Democratic-leaning voters or last-minute advertising could widen or compress the final spread.