Close InsiderAdvantage poll moves South Carolina Senate to 17% for Andrews

An InsiderAdvantage survey of 1,200 likely voters, fielded September 28-29, found Republican incumbent Darline Graham at 46% and Democrat Annie Andrews at 45%, with 3% choosing another option. A one-point gap in a single poll is a close race, not a lead for either candidate.

The poll changed our forecast. Our model now gives Andrews a 17 in 100 chance of winning the seat, up from 8% in our run at 9:02 AM ET this morning. Graham's chance falls from 92% to 83%. Our model's average margin moves from R+7.9 to R+5.3.

The range of plausible outcomes shifted with it. Our model's 5th-to-95th percentile band now runs from R+14.4 to D+3.9, compared with R+17.0 to D+1.2 before this poll. Most of that band still sits on the Republican side, and our model's average margin remains wider than the gap in this survey.

The race matters for the chamber. Our model gives Democrats a 55% chance of winning Senate control and Republicans 44%, with an average of 50.7 Democratic seats. Democrats need 51 seats for a majority. Republicans need 50, because the vice president is a Republican and a 50-50 tie goes to them. There are 32 days until the election on November 3.