Our poll-based analysis began in 2000 with the Bush/Gore presidential election. In 2010, we began our Senate analysis. Using data from the most recent poll, we determine the probability for the Democrat and the Republican candidate in each race. We use these individual race probabilities to calculate the odds for every possible combination of outcomes to calculate each party's odds of winning. To include a poll for a Senate race, it must meet the following conditions:
Democrats and Republicans are evenly split in the Senate: 50 Senators caucus with each party. Therefore, Democrats control the Senate as Vice-President Harris casts the tie-breaker. This year there are 35 Senate seats which are up for election, 21 will be defended by Republicans and 14 by Democrats; 29 Republicans and 36 Democrats are not up for re-election. To gain control of the Senate, Republicans will need a net gain of at least one seat, otherwise Democrats will keep control of the Senate.
Our poll-based method determines the race probabilities for each party's candidate based on the latest poll data for each race. From the individual race odds, we calculate the overall odds for each party to win from over 34 billion possible outcomes. Our poll-based method has correctly projected the party to control the Senate since 2010, when we began analyzing the Senate.
Here are the current poll-based probabilities for each Senate race:
Here is our current poll-based projection for the Senate based upon the individual race odds:
Here is our poll-based Senate Tracker: