Adam Pearce
NYT confidence intervals show the 5%, 25%, 50%, 75% and 95% percentiles of predicted vote margins.
The Washington Post doesn’t directly calculate confidence intervals for vote margins. The displayed bands are calculated using the upper vote total estimate from one party and the lower vote total estimate from the other party:
dem['upper_0.9'] - gop['lower_0.9']/(dem['upper_0.9'] - gop['lower_0.9'])