Why was 2020 a depolarization election?

Question

A lot of attention was given to the fact that Trump did better with Democratic leaning groups especially Hispanics, while Biden did better with Republican leaning groups like married men and evangelicals. I think that we should look at this beyond the demographic level and look at it this way: the blue got redder and vice versa.

You could see this same effect at the county and even state level. Five out of seven electoral units that saw two party vote swings towards Trump (California, Hawaii, Illinois, New York and Washington DC) had higher than average vote shares for Biden and thus Hillary Clinton (and all significantly higher than average at that), with the other two being considered swing states (Nevada and Florida). West Virginia and Wyoming, the two most Republican states in both 2016 and 2020, moved 5% and 7% towards Biden, more than twice the national shift.

Here is an image that shows the correlation between swing and 2020 vote share (it was -43%):

What caused the apparent depolarization in the 2020 presidential election? Was it higher turnout bringing out voters that vote in unexpected ways? People switching sides? Some combination or something else?

Answer 1

The 2020 Election Was Not Depolarizing

I disagree with your premise. The 2020 election was not a depolarizing election.

Both 2016 and 2020 were incredibly polarized elections relative to prior years and any distinction between 2016 and 2020 is more or less trivial and misses the forest for the trees.

While there were slight tweaks to the outcomes in some swing states that changed the result, the overall shifts were modest in magnitude everyplace that it mattered. The evidence supporting this conclusion includes the following points.

Coalition Changes Can Inaccurately Look Like Depolarization

Also, redrawing coalitions does not imply depolarization. Democrats have in recent elections shed working class voters while picking up college educated voters from Republicans. This has certainly happened.

More Demographically Polarized Voters

But that doesn't make partisan divides any less stark. The electorate is more divided by ideology, by race, by gender, by age, by geography (especially at a county or smaller level), and by religion than ever (see 2020 exit polling from multiple sources summarized here).

Consider, for example, the extent to which the nation has become polarized politically along economic lines:

More Polarized Voter Ideologies

In general, we have gradually shifted over the last decade or two from a political system in which voters are ideologically situated on a bell curve of ideology, with elected officials being more bimodal with moderate left and moderate right peaks, to one in which the distribution of voters by ideology increasingly mirrors that ideological distribution of federal elected officials in the U.S.

More Polarized Members Of Congress

For example, both the House and Senate have no ideological overlap between the parties (something that was not true until recently).

Record Low District Splitting

Similarly, the total number of split districts in 2020 was 16 (3.7% of Congressional Districts). This is the lowest level of district-splitting, both in percentage and absolute terms, since 1920, a full century earlier. That year, 11 out of 344 districts produced a split result (3.2% of Congressional Districts). In 2016 and 2012, 35 and 26 districts (respectively) split their tickets.

Answer 2

You have missed a very important point here, which is that both the 2016 and 2020 Presidential elections were less about politics than about the personalities of the candidates.

In 2016, you had many voters who were unwilling to vote for a woman, and one without much in the way of credentials or personal appeal. Against her, you have someone with a familiar name, who had spent his life creating a false impression of business competence.

Four years later, that person had demonstrated his actual lack of competence, most prominently in mishandling the COVID pandemic, and had other aspects of his character exposed. Running against him you had someone with a long record of moderate competence, and a reasonably likeable personality.

Those differences, not politics, were what tipped the elections. They were personal rejections of the candidates, more than of their politics. This is demonstrated by the results of the House and Senate elections, where political results were much closer.