Alaska at-large forecast moves toward Begich as the Democratic line goes to zero

Our model's numbers for Alaska's at-large House district changed shape over the past week. In the run of August 18, it gave a Democrat a 72 percent chance and Republican incumbent Nick Begich III 28 percent. In the run of August 25, the Democratic chance is zero, independent Bill Hill has a 63 in 100 chance and Begich has 37 percent. That is a 72.3-point drop in Democratic win probability over seven days, and the candidate list our model is now running contains no Democrat.

The underlying margin moved less. Our model's mean margin was I+6.1 a week ago and is I+3.4 now, a shift of 2.7 points toward Begich. The 5th-to-95th percentile range tightened at both ends, from R+11.1 to I+23.2 last week to R+13.2 to I+20.1 this week.

No new survey of the district arrived in between. The most recent poll in our average is still the Data for Progress survey of 605 likely voters fielded July 28 to August 4, which had Begich at 47 percent and the independent at 37 percent. That poll was already in the average when we wrote about this seat on August 18. So the week's movement is a change in our model's own accounting of the race rather than a response to fresh polling, and we are not going to assign it a cause the payload does not support.

Nationally, our model gives Democrats a 93 percent chance of winning House control, with a mean of 240.5 seats against the 218 needed. One caveat on that figure is ours to own: our simulation correlates error nationally, by census division, by state and within each district, but we have no cluster data to correlate demographically similar districts across state lines. Without that term, the House control number is marginally firmer than it should be.