Snapshot probability distribution of all possible outcomes calculated from current state polls. The blue bars represent combinations of outcomes leading to Democratic control. The red bars represent Republican control. This a snapshot, based on conditions today, of the polled demographic. Because the histogram is based on all available polls, it includes pollster-to-pollster “house effects” as part of the variation. On Election Eve its center should be close to or at the final election outcome.
2014: When looking at the 2014 distribution (which is possible using our wayback functionality in the left sidebar), the green bar indicates outcomes in which Democrats and Independents control 50 votes, and independent Greg Orman of Kansas provides one of the votes. In this case Orman’s choice of caucus will determine control of the chamber.
In midterm election years (2010, 2014, 2018…), the histogram does not take into account the possibility of midterm polling bias, which adds further uncertainty of +/- 2.5%.