New WA-3 poll finds a close race and trims Gluesenkamp Perez's odds in our model

A DHM Research survey for Oregon Public Broadcasting of 543 likely voters in Washington's 3rd District, fielded September 17-27, found Republican John Braun at 48% and Democratic Rep. Marie Gluesenkamp Perez at 47%. A one-point gap in a sample of that size is a close race, not a lead for either candidate.

The poll moved our forecast. Our model now gives Gluesenkamp Perez an 89 in 100 chance of winning the seat, down from 96% in the run published earlier today at 12:32 PM ET. Braun's chance rose from 4% to 11%. Our expected margin fell from D+14.6 to D+10.5.

The range of plausible outcomes also shifted. In our earlier run, the 5th-to-95th percentile span ran from D+0.4 to D+28.7, so nearly every simulated result favored the incumbent. It now runs from R+3.7 to D+24.8, which puts a Braun win inside that range. Our model still favors Gluesenkamp Perez by a wide margin on average, but the new survey is the closest reading of the district in this payload, and it narrows the gap between our estimate and a competitive race.

The change in one district does little to the national House picture. Our model gives Democrats a 98% chance of winning a majority, with an average of 245.4 Democratic seats against the 218 needed. That figure is somewhat firmer than it should be. Our simulation correlates error nationally, by census division, by state and within each district, but it does not link demographically similar districts in different places, because we lack the data to do so.