[24 OCT 2020]
My previous analysis of the Senate races was a few weeks ago. If the election had been held in early October, the Senate would have almost certainly gone to the Democrats with, on average, 54 seats.
How have things changed? Not much. After 100,000 simulated elections, Democrats have a Senate majority 99,878 times, there were 122 ties, and Republicans never took control of the Senate. Democrats have a 100.0% probability of controlling the Senate if Vice President Joe Biden takes the White House. Republicans have about a 0.1% probability of controlling the Senate if President Donald Trump is reelected.
Some states have shown minor movement as more polling comes in. Going from 2 to 4 polls in Kansas has flipped the state from red to blue. Republican Roger Marshall was ahead with 82% chance of winning three weeks ago. Now, Democrat Barbara Bollier would have a 63% probability of winning that election today.
In the Montana race where Democrat Steve Bullock is challenging Republican Sen. Steve Daines, the race has swung further into Daines favor. He went from a 57% chance of Daines prevailing three weeks ago to an 80% chance now.
The Georgia seat 2 special election now has 5 polls that, in addition to polling the main event on Nov 3, put the top Democrat, Raphael Warnock, head to head against the top Republicans. I am using polls that assume Republican Sen. Kelly Loeffler will go up against Warnock in the 2-candidate runoff. But the results don’t change if Republican Doug Collins ends up in the runoff election. In both cases Warnock has a high probability of winning.
Here is the distribution of Senate seats from the simulations:*
This graphs shows the probability of at least each number of seats controlled by the Democrats:*
- 100000 simulations: Democrats control the Senate 100.0%, Republicans control the Senate 0.0%.
- Average ( SE) seats for Democrats: 54.2 ( 1.3)
- Average (SE) seats for Republicans: 45.8 ( 1.3)
- Median (95% CI) seats for Democrats: 54 (52, 57)
- Median (95% CI) seats for Republicans: 46 (43, 48)
Expected outcomes from the simulations:
- Democratic seats w/no election: 34
- Independent seats w/no election: one
- Republican seats w/no election: 30
- Contested Democratic seats likely to remain Democratic: 11
- Contested Republican seats likely to remain Republican: 16
- Contested Democratic seats likely to switch: one
- Contested Republican seats likely to switch: seven
This table shows the number of Senate seats controlled for different criteria for the probability of winning a state:* Safe>0.9999, Strong>90%, Leans>60%, Weak>50%
|Threshold||Safe||+ Strong||+ Leans||+ Weak|
This table summarizes the results by state. Click on the poll number to see the individual polls included for a state.
|State||@||polls||size||Democrat||Republican||% wins||% wins|
@ Current party in office
& An older poll was used (i.e. no recent polls exist).
*Analysis assume that the two independent candidates will caucus with the Democrats.
Details of the methods are given in the FAQ.