Maine Senate model moves 13.6 points toward Collins over five days

Our model's estimate of the Maine Senate race has moved toward the Republican, Sen. Susan Collins. In the run of September 23 at 6:02 PM ET, it gave Democrat Troy Jackson a 75% chance of winning. As of September 28, our model gives Jackson a 62 in 100 chance. That is a change of 13.6 points of Democratic win probability over five days.

The projected margin moved with it. Our model's mean margin fell from D+4.0 to D+1.7. Its range between the 5th and 95th percentiles shifted from R+5.6 to D+13.5 in the earlier run to R+7.7 to D+11.0 now. Both ranges include outcomes in which either candidate wins.

Four Maine polls figure in our updates since that run, and they do not point in one direction. A New York Times/Siena University survey for the Portland Press Herald of 619 likely voters, fielded September 15-22, had Collins at 48.66 percent and Jackson at 45.92 percent, a close race. A University of New Hampshire survey of 1,301 likely voters, fielded September 17-21, had Jackson at 51 percent and Collins at 47 percent. A University of Massachusetts Lowell/YouGov survey of 650 likely voters, fielded August 28 to September 14, had Jackson at 48 percent and Collins at 43 percent. An InsiderAdvantage survey of 1,200 likely voters, fielded September 22-23, had Jackson at 46.4 percent and Collins at 45.6 percent, also a close race.

The payload does not break the net shift down by poll, and this note does not assign it to any single survey. What it shows is a five-day move of 13.6 points toward Collins across a set of polls ranging from a close race to a five-point Jackson edge.

The race matters for the chamber. Our model gives Democrats a 54% chance of winning Senate control, which requires 51 seats; a 50-50 tie goes to the Republicans, because the vice president is a Republican. Our model's mean is 50.7 Democratic seats.