Our forecast uses polling data that we downloaded from FiveThirtyEight on October 30. In 10,000 simulated elections, Democrats gain control of the Senate about 85% of the time. We forecast 52.7 Democratic seats, with a standard deviation of about 1.4 seats across our simulated elections.

For the case of a tie in the Senate (50 seats for each party), we use our presidential forecasts to determine which party wins control. Because we do not forecast the vote margin in the Georgia special election (since it has more than two main candidates), we assigned this race an equal chance of voting Republican or Democratic when we created our Senate-seat distribution.

Our forecast uses polling data that we downloaded from FiveThirtyEight on October 27. In 10,000 simulated elections, Democrats gain control of the Senate about 86% of the time. We forecast 52.6 Democratic seats, with a standard deviation of about 1.4 seats across our simulated elections.

For the case of a tie in the Senate (50 seats for each party), we use our presidential forecasts to determine which party wins control. Because we do not forecast the vote margin in the Georgia special election (since it has more than two main candidates), we assigned this race an equal chance of voting Republican or Democratic when we created our Senate-seat distribution.

Our forecast uses polling data that we downloaded from FiveThirtyEight on October 25. In 10,000 simulated elections, Democrats gain control of the Senate about 87% of the time. We forecast 52.7 Democratic seats, with a standard deviation of about 1.4 seats across our simulated elections.

For the case of a tie in the Senate (50 seats for each party), we use our presidential forecasts to determine which party wins control. Because we do not forecast the vote margin in the Georgia special election (since it has more than two main candidates), we assigned this race an equal chance of voting Republican or Democratic when we created our Senate-seat distribution.

Our forecast uses polling data that we downloaded from FiveThirtyEight on October 21. We simulate 10,000 stochastic elections, and Democrats gain control of the Senate about 86% of the time. For the case of a tie in the Senate (50 seats for each party), we use our presidential forecasts to determine which party wins control.

Because we do not forecast the vote margin in the Georgia special election (since it has more than two main candidates), we assigned this race an equal chance of voting Republican or Democratic when we created our Senate-seat distribution.

Our forecast uses polling data from FiveThirtyEight that we gathered on October 9 at 18:13 CDT. Unlike our prior forecasts, we now treat South Carolina individually instead of including it as part of the Red superstate. Interestingly, the model forecasts South Carolina as leaning slightly Democratic. Otherwise, the vote margin that we project in each state has changed very little since our last forecast.

We simulate 10,000 stochastic elections, and Democrats gain control of the Senate about 86% of the time. For the case of a tie in the Senate (50 seats for each party), we use our presidential forecasts to determine which party wins control.

Because we do not forecast the vote margin in the Georgia special election (since it has more than two main candidates), we assigned this race an equal chance of voting Republican or Democratic when we created our Senate-seat distribution.

Using polling data from FiveThirtyEight that we gathered on September 28, 2020, at 22:21 CDT to determine our model parameters, we find that Montana, Kansas, and Georgia have the tightest senatorial races. In our forecasts below, we simulate 10,000 stochastic elections and show the mean vote-margin outcomes. The yellow lines indicate the range that encompasses the middle 80% of our simulated elections. Many of these lines cross zero, suggesting close elections.