Election 2020: Election day Senate analysis

Senate Democrats*	Senate Republicans
greater than 99.9% probability	less than 0.1% probability
Mean of 53 seats	Mean of 47 seats

Since yesterday’s analysis, about 20 new polls have come out. The results have not changed much. This is my final analysis of the for the Senate races.

After 100,000 simulated elections, Democrats have a Senate majority 99804 times, there were 196 ties, and Republicans control the Senate 0 times. This analysis suggests that Democrats will almost certainly control the Senate in 2021.

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: 53.3 ( 1.1)
• Average (SE) seats for Republicans: 46.7 ( 1.1)
• Median (95% CI) seats for Democrats: 53 (51, 55)
• Median (95% CI) seats for Republicans: 47 (45, 49)

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
Safe Democrat	49
Strong Democrat	2	51
Leans Democrat	2	2	53
Weak Democrat	0	0	0	53
Weak Republican	0	0	0	47
Leans Republican	3	3	47
Strong Republican	5	44
Safe Republican	39

This table summarizes the results by state. Click on the poll number to see the individual polls included for a state.

		#	Sample	Percent	Percent	Democrat	Republican
State	@	polls	size	Democrat	Republican	% wins	% wins
AL		5	3548	43.6	56.4	0.0	100.0
AK		2	1404	48.6	51.4	21.7	78.3
AZ		25	17135	53.0	47.0	100.0	0.0
AR		2	1086	33.2	66.8	0.0	100.0
CO		6	3715	55.2	44.8	100.0	0.0
DE		1&	712	67.8	32.2	100.0	0.0
GA		16	13003	50.6	49.4	82.6	17.4
GA		4	2470	54.9	45.1	100.0	0.0
ID		1&	487	34.1	65.9	0.0	100.0
IL		2	1289	65.6	34.4	100.0	0.0
IA		14	9688	50.4	49.6	72.9	27.1
KS		3	2512	48.0	52.0	8.9	91.1
KY		5	2561	44.9	55.1	0.0	100.0
LA		1&	680	38.8	61.2	0.0	100.0
ME		4	3156	51.8	48.2	92.1	7.9
MA		2	1474	69.2	30.8	100.0	0.0
MI		29	22523	53.4	46.6	100.0	0.0
MN		11	7670	54.6	45.4	100.0	0.0
MS		2	1032	47.2	52.8	9.0	91.0
MT		6	4198	49.3	50.7	26.0	74.0
NE		1	395	27.3	72.7	0.0	100.0
NH		4	3090	57.7	42.3	100.0	0.0
NJ		2	1194	65.3	34.7	100.0	0.0
NM		1	1133	54.2	45.8	97.9	2.1
NC		28	22416	51.9	48.1	100.0	0.0
OK		1	5102	39.6	60.4	0.0	100.0
OR		1&	849	61.1	38.9	100.0	0.0
RI		0	0			(100)	(0)
SC		7	5492	49.1	50.9	18.1	81.9
SD		1	455	41.1	58.9	0.2	99.8
TN		2	982	39.1	60.9	0.0	100.0
TX		18	18716	47.0	53.0	0.0	100.0
VA		6	4111	58.6	41.4	100.0	0.0
WV		1&	386	38.3	61.7	0.2	99.8
WY		0	0			(0)	(100)

^@ 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.

The most recent analysis in this match-up can be found from this page.