South Carolina Senate moves to 19 in 100 for the Democrat after a near-tied poll

Our forecast of the South Carolina Senate race has moved toward the Democrat, Annie Andrews, over the past week. On September 3 at 6:32 PM ET our model gave her an 8 percent chance of winning. As of September 10 at 6:02 PM ET it gives her 19 in 100, a gain of 11.1 points across seven days. The Republican incumbent, Darline Graham, is at 81 percent.

The mean margin moved with it. Our model had the race at R+8.9 last week and now has it at R+5.3. The middle of our simulated range shifted too: the 5th-to-95th percentile band was R+19.3 to D+1.5 and is now R+15.5 to D+4.7. That is a band that still contains comfortable Republican outcomes and a narrow Democratic one.

One survey arrived between the two runs. InsiderAdvantage polled 1,200 likely voters on September 8 and 9 and found the Republican at 45.1 percent and Andrews at 43.2 percent. The gap there is under two points, so the poll is best read as a close race rather than a lead for either candidate. It is the only new polling in the payload for this race, and the direction of our movement is consistent with it.

Nationally, our model gives Democrats a 49 percent chance of Senate control and Republicans 50 percent, with a mean of 50.2 Democratic seats. Democrats need 51 seats for control and Republicans need 50, because the vice president is a Republican and a 50-50 tie goes to the Republicans. On that arithmetic, a seat our model still rates 81 percent Republican matters to the national picture mainly in the tail where it turns. Our generic-ballot average stands at D+6.7 across 25 polls in a 45-day window.