Jackson up four in UNH poll; Maine forecast moves to 62 percent

A University of New Hampshire survey of 1,301 likely voters, fielded September 17-21, put Democrat Troy Jackson at 51 percent and Republican incumbent Susan Collins at 47 percent. The poll's margin of error is not included in what we have, so the four-point gap is best read as a close race with Jackson on the better side of it.

Our model now gives Jackson a 62 in 100 chance of winning the seat, up from 56 percent in our previous run at 4:32 PM ET on September 24. The mean margin moved from D+0.9 to D+1.7. The spread barely narrowed: our 5th-to-95th percentile range runs from R+7.7 to D+11.2, against R+8.6 to D+10.4 before. That is a race our model still treats as genuinely uncertain 40 days out, with outcomes on both sides of the line well inside the plausible range.

The direction of the move is worth noting more than its size. Our published estimate for Maine has crossed back and forth this month, and the UNH numbers pull it toward Jackson rather than establishing anything new. A six-point shift in win probability from a single poll in a race our model already had within two points of even is the kind of adjustment that reverses on the next survey.

Maine matters to the national picture because our Senate estimate is close. Our model gives Democrats a 53 percent chance of winning Senate control and a mean of 50.6 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. The House is a different proposition: we give Democrats a 98 percent chance of reaching the 218 seats needed there, with a mean of 245.7. One caveat on that figure is ours to own — our simulation correlates error nationally, by census division, by state and by district, but we have no data to correlate demographically similar districts across regions, so the House number is marginally firmer than a fuller model would make it.