This year’s Electoral College map may show another ‘blue shift.’ Here’s why

The counting of ballots can take longer in some places than in others.

In presidential elections, that difference can cause a candidate’s early advantage in a state to change as more localities report their results in the hours and, sometimes, days after polls close on Election Day.

In 2020, the phenomenon known as the “red mirage” or “blue shift” turned the hue of several seemingly red states — where then-Republican President Donald Trump appeared to be in the lead over the then-Democratic candidate Joe Biden — blue.

Trump and his allies responded by linking that change in states including Arizona, Georgia, Michigan, Nevada and Pennsylvania to baseless claims of widespread voter fraud involving mail-in ballots.

In fact, however, it stemmed from partisan divides in where voters live and their preferred way of casting ballots, plus, in some states, laws that slow the tallying of votes.

Republicans in smaller counties voting in person vs. Democrats in larger counties voting by absentee ballot

There are two trends that help explain the range of reporting speeds for election results:

• Voters in urban, more densely populated communities are generally more Democratic-leaning, and smaller, rural communities are often home to more Republican-leaning voters.

• Republicans tend to prefer voting in person, while Democrats have driven the rise of mail voting since the pandemic election of 2020, recent elections have shown. (A new NPR/PBS News/Marist poll indicates the trend is likely to continue in the 2024 general election.)

An analysis of the 2020 election by the MIT Election Data and Science Lab concluded that the differences in how quickly counties reported their results were “driven by the fact that smaller and more rural counties,