Big Data Poll finds Ohio Senate race close; our Brown estimate eases to 78%

A new Big Data Poll survey for the Public Polling Project, fielded September 26-27, finds the Ohio Senate special election close. Among 680 likely voters, Democrat Sherrod Brown had 46.3% and Republican Sen. Jon Husted had 42.6%. Among 735 registered voters in the same survey, Brown had 45.2% and Husted 41.2%.

Both samples put Brown ahead by about four points. The payload does not report the poll's margin of error, but gaps of that size in samples of this size are not clear leads. The race in this survey is close.

Our model now gives Brown a 78 in 100 chance of winning, down from 80% in the run earlier today. Our projected margin moved from D+4.8 to D+4.3. Our range of likely outcomes, from the 5th to the 95th percentile, now runs from R+5.0 to D+13.6, compared with R+4.4 to D+14.0 before.

The change is small. A margin near four points is roughly what our model already expected, and slightly below its previous mean, so the new numbers pulled the estimate a little toward Husted rather than changing the picture. Earlier today, our estimate had moved to 80% after a Marist poll; this survey takes back part of that movement.

The seat matters for the chamber. Our model gives Democrats a 58% chance of winning Senate control, with an average of 50.9 Democratic seats across our simulations. Democrats need 51 seats for control. Republicans need 50, because the vice president is a Republican and a 50-50 tie goes to them.