This is part 1 of a two-part MIT News series on voting research and the 2020 election. When you watch election returns on Nov. 3, keep this in mind: In some U.S. states, it will take days to count all the ballots, and the winner might only be clear later, rather than sooner. Four straight U.S. presidential elections have featured a “blue shift,” in which the post-Election Day ballot count helped the Democratic Party candidate gain ground on the Republican nominee. And the GOP’s Richard Nixon twice enjoyed a “red…