Election 2020: Biden is still gaining on Trump

Biden	Trump
> 99.9% probability of winning	< 0.1% probability of winning
Mean of 389 electoral votes	Mean of 149 electoral votes

My previous analysis was before the conventions. Now, roughly a month after the conventions, any movement from the conventions should become apparent.

To assess an election held today, we simulate 100,000 elections using the past month of polls as “current” and only using older polls if there are no current polls. From that exercise, Joe Biden won all 100,000. Biden received (on average) 389 to Donald Trump’s 149 electoral votes, a modest improvement for Biden from the 378 to 160 electoral vote lead he had at the end of July. In an election held now, Biden would have a greater than 99.9% probability of winning.

The long term trends in this race can be seen from a series of elections simulated every seven days using polls from 18 Sep 2019 to 18 Sep 2020, and including polls from the preceding month (FAQ).

Clearly, Biden has the lead and the momentum at this point in the election season, with his expected electoral vote total tending to climb since January. Details for the the most recent simulation is found below the fold.

Here is the distribution of electoral votes [FAQ] from the simulations for today’s results:

Ten most probable electoral vote outcomes for Biden (full distribution here):

• 407 electoral votes with a 4.51% probability
• 389 electoral votes with a 3.58% probability
• 413 electoral votes with a 3.51% probability
• 395 electoral votes with a 2.56% probability
• 392 electoral votes with a 2.53% probability
• 408 electoral votes with a 2.52% probability
• 406 electoral votes with a 2.46% probability
• 403 electoral votes with a 2.40% probability
• 398 electoral votes with a 2.23% probability
• 391 electoral votes with a 2.17% probability

The single most likely outcome is a 407 to 131 victory for Biden. Many, if not all, of those outcomes would be considered a landslide victory depending, of course, on the definition of a landslide.

Further results from 100,000 simulations:

• Biden wins greater than 99.9%, Trump wins less than 0.1%.
• Average (SE) EC votes for Biden: 389.4 (20.6)
• Average (SE) EC votes for Trump: 148.6 (20.6)
• Median (95% CI) EC votes for Biden: 392 (344, 419)
• Median (95% CI) EC votes for Trump: 146 (119, 194)

Each column of this table shows the electoral vote total aggregated by different criteria for the probability of winning a state (Safe=100%, Strong=90%+, Leans=60%+, Weak=50%+):

Threshold	Safe	+ Strong	+ Leans	+ Weak
Safe Biden	274
Strong Biden	34	308
Leans Biden	99	99	407
Weak Biden	0	0	0	407
Weak Trump	0	0	0	131
Leans Trump	13	13	131
Strong Trump	66	118
Safe Trump	52

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

	1	1	EC	#	Total	%	%	Biden	Trump
	6	2	Votes	polls	Votes	Biden	Trump	% wins	% wins
AL			9	1*	572	38.3	61.7	0.0	100.0
AK			3	1*	831	46.8	53.2	9.6	90.4
AZ			11	14	10525	52.6	47.4	100.0	0.0
AR			6	1*	799	48.9	51.1	32.8	67.2
CA			55	3	2370	64.4	35.6	100.0	0.0
CO			9	4	2675	55.5	44.5	100.0	0.0
CT			7	2*	1494	62.5	37.5	100.0	0.0
DE			3	1	675	61.0	39.0	100.0	0.0
DC			3	0				(100)	(0)
FL			29	17	22205	52.3	47.7	100.0	0.0
GA			16	6	6230	51.1	48.9	88.3	11.7
HI			4	1*	829	65.9	34.1	100.0	0.0
ID			4	1	565	36.6	63.4	0.0	100.0
IL			20	0				(100)	(0)
IN			11	1	950	42.4	57.6	0.1	99.9
IA			6	1	736	48.9	51.1	34.3	65.7
KS			6	2*	1879	46.2	53.8	1.3	98.7
KY			8	1	1117	39.6	60.4	0.0	100.0
LA			8	2*	1668	43.4	56.6	0.0	100.0
ME			2	3	2517	59.4	40.6	100.0	0.0
ME1			1	3	1416	65.2	34.8	100.0	0.0
ME2			1	4	1476	52.0	48.0	85.8	14.2
MD			10	1*	765	62.6	37.4	100.0	0.0
MA			11	1	745	69.5	30.5	100.0	0.0
MI			16	13	11756	53.7	46.3	100.0	0.0
MN			10	9	5897	54.6	45.4	100.0	0.0
MS			6	1*	576	44.8	55.2	4.2	95.8
MO			10	2	1410	45.2	54.8	0.5	99.5
MT			3	2	1112	46.8	53.2	6.8	93.2
NE			2	0				(0)	(100)
NE1			1	1*	376	48.9	51.1	39.8	60.2
NE2			1	1*	477	53.7	46.3	87.0	13.0
NE3			1	0*				(0)	(100)
NV			6	1	407	52.3	47.7	74.4	25.6
NH			4	1	387	51.7	48.3	68.4	31.6
NJ			14	1	465	59.1	40.9	99.8	0.2
NM			5	1	1044	58.0	42.0	100.0	0.0
NY			29	1	977	66.3	33.7	100.0	0.0
NC			15	18	16294	50.4	49.6	77.2	22.8
ND			3	2*	942	40.3	59.7	0.0	100.0
OH			18	4	5083	50.3	49.7	61.9	38.1
OK			7	1	459	37.0	63.0	0.0	100.0
OR			7	1	452	56.6	43.4	98.0	2.0
PA			20	15	14854	52.6	47.4	100.0	0.0
RI			4	0				(100)	(0)
SC			9	1	930	46.9	53.1	8.5	91.5
SD			3	0				(0)	(100)
TN			11	2*	1407	43.6	56.4	0.0	100.0
TX			38	6	9600	50.6	49.4	78.3	21.7
UT			6	1	880	39.8	60.2	0.0	100.0
VT			3	0				(100)	(0)
VA			13	1	637	58.1	41.9	99.7	0.3
WA			12	1*	499	69.1	30.9	100.0	0.0
WV			5	1*	495	33.3	66.7	0.0	100.0
WI			10	21	15799	53.6	46.4	100.0	0.0
WY			3	0				(0)	(100)

^* An older poll was used (i.e. no recent polls exist).

Details of the methods are given in the FAQ.

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