Election 2020

[pbrower2a]

Here, according to Nate Silver in The Signal and the Noise, are the probabilities of a Senate candidate winning (1998 to 2008) with a certain lead (1, 5, 10, and 20 points) at one year, six months, three months, one month, one week, and one day. Because statewide races for President are much like statewide races for the Senate -- with the qualification that Presidential nominees do not usually make appearances where they see themselves losing -- unless they really are losing nationwide. I see this as about as good an estimate of a Presidential nominee winning a state as anything, except that the chances of winning a long-shot (Hey -- Trump has a 2% chance of winning Illinois!) or of course the opposite are likely overstated. This assumes of course an active and competent campaign.  

Time to election  |1 point|5 points||10 points|20 points|
one day............. |...64%|....95%|.....99.7%|.99.999%|
one week........... |...60%|....89%|.......98%|...99.97%|
one month......... |...57%|....81%|.......95%|.....99.7%|
three months..... |...55%|....72%|.......87%|........98%|
six months..........|...53%|....66%|.......79%|.......93%|
one year.............|....52%|...59%|.......67%|.......81%|



We are one month away from Election Day, so the line in boldface applies:

Time to election  |1 point|5 points||10 points|20 points|
one day............. |...64%|....95%|.....99.7%|.99.999%|
one week........... |...60%|....89%|.......98%|...99.97%|
one month......... |...57%|....81%|.......95%|.....99.7%|
three months..... |...55%|....72%|.......87%|........98%|
six months..........|...53%|....66%|.......79%|.......93%|
one year.............|....52%|...59%|.......67%|.......81%|

Things are likely worse for Trump in states in which he has gone behind by 10% or more. But sticking to this model I can interpolate on a assumption that the probability rises in a linear fashion, which may itself be an understatement in much of the range. Arbitrarily I am going to treat any 15% lead one month away as giving either nominee a 99%+ chance of winning, and I am not going to make distinctions above 99%.

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