Our Idaho margin widens again while the odds stay pinned

The two most recent polls of Idaho's Senate race point in different directions. A Peak Insights survey of 500 likely voters, fielded August 11-13, put Republican incumbent Jim Risch at 52 percent, with 9 percent for an independent and 2 percent for other candidates. A Bullfinch Group survey of 608 likely voters, fielded August 4-7, had Risch at 34 percent and independent Todd Achilles at 30 percent, with 4 percent for others — close, on a sample that size, rather than a lead.

Our model now puts the mean margin at R+30.2, out from R+23.5 in the previous run earlier this afternoon. The 5th-to-95th percentile band runs from R+48.7 to R+11.2, wider on the Republican side than the R+33.9 to R+12.8 range it replaced. The probability did not move: our model gives Risch a 100 percent chance and the Democratic column a 0 in 100 chance, unchanged.

The rest of the Idaho data is older and no more settled. The Bullfinch Group's May 29 to June 1 poll of 774 registered voters had Risch 40, Achilles 36 in a head-to-head; the same sample gave Risch 50 to 33 against a generic Democrat, and 41-18-15 in a three-way with Achilles and a Democrat. A Public Policy Polling survey of 639 registered voters, fielded March 16-17, had Risch 48, Achilles 34. Spreads across those five results range from four points to 17.

Nationally, our model has the generic ballot at D+6.5 across 28 polls in a 45-day window. It gives Democrats a 49 percent chance of Senate control and Republicans 50 percent, with a mean of 50.2 Democratic seats against the 51 Democrats need; Republicans need 50, because a 50-50 tie goes to them on the vice president's vote. Idaho is not among the seats that decide that.