Read on Twitter
Because I am getting Qs on this today, useful to run down all the many times that US presidential election results have taken days, weeks, months to call. Here are a few of the great opeds by historians and others over the past months explaining this history 
Here's @KevinMKruse & @EllenLWeintraub, reminding us back in May that taking time to count is a *good* thing https://www.nytimes.com/2020/05/18/opinion/2020-election-results-delay.html
Here's @lmchervinsky last week on how Election Night results are a relatively new phenomenon https://www.governing.com/now/History-Teaches-Us-Election-Delays-Are-Nothing-New.html
Here's @RichardKreitner on 1876, the wildest of wide electoral rides, stretching on into March 1877 (ending in a compromise with lasting, devastating consequences) https://www.washingtonpost.com/outlook/2020/09/11/election-our-past-that-blares-warning-2020/
Here's @ted_widmer on 1860, which he correctly describes as "the most toxic campaign in American history" https://www.nytimes.com/2020/10/30/opinion/lincoln-trump-1860-2020.html
Expect more to come, but in the meantime I will leave you with Walter Cronkite and the UNIVAC in 1952, right about the first time that Election Night calls became a thing. (Thanks, computers!) https://www.npr.org/sections/alltechconsidered/2012/10/31/163951263/the-night-a-computer-predicted-the-next-president
