One of the most heavily contested voting-policy issues in the 2020 election, in both the courts and the political arena, was the deadline for returning absentee ballots. Now that it’s possible to get data on this issue, I put together an essay for The Conversation that looks at what we can learn about how much these deadlines — including last-minute changes in them — did or did not lead to significant numbers of ballots coming in too late to be valid.

Here is a summary of what I found:

Perhaps surprisingly, the number of ballots that came in too late to be valid was extremely small, regardless of what deadline states used, or how much that deadline shifted back and forth in the months before the election. The numbers were nowhere close to the number of votes that could have changed the outcome of any significant race.

One of the focal points of these battles was Wisconsin, which led to the Supreme Court’s most controversial decision regarding the general election:

In Wisconsin, state law required absentee ballots to be returned by Election Night. The federal district court ordered that deadline extended by six days. But the Supreme Court, in a 5-3 decision, blocked the district’s court order and required the deadline in the state’s election code to be respected.

Writing for the three dissenters, Justice Elena Kagan invoked the district court’s prediction that as many as 100,000 voters would lose their right to vote, through no fault of their own, as a result of the majority’s ruling that the normal state-law deadline had to be followed. Commentators called this a “disastrous ruling” that “would likely disenfranchise tens of thousands” of voters in this key state.

The post-election audit now provides perspective on this controversy that sharply divided the court. Ultimately, only 1,045 absentee ballots were rejected in Wisconsin for failing to meet the Election Night deadline. That amounts to 0.05% ballots out of 1,969,274 valid absentee votes cast, or 0.03% of the total vote in Wisconsin.

Minnesota was another state that saw prolonged legal battles over this issue:

The fight over ballot deadlines in Minnesota was even more convoluted. If voters were going to be confused anywhere about these deadlines, with lots of ballots coming in too late as a result, it might have been expected to be here.

State law required valid ballots to be returned by Election Night, but as a result of litigation challenging that deadline, the secretary of state had agreed in early August that ballots would be valid if they were received up to seven days later.

But a mere five days before the election, a federal court pulled the rug out from under Minnesota voters. On Oct. 29, it held that Minnesota’s secretary of state had violated the federal Constitution and had no power to extend the deadline. The original Election Night deadline thus snapped back into effect at the very last minute.

Yet it turns out that only 802 ballots, out of 1,929,945 absentees cast (0.04%), were rejected for coming in too late.

For comparison, I looked at a battleground state where the Election Day deadline remained fixed throughout the run-up to the election:

Among battleground states, Michigan provides an example. Only 3,328 ballots arrived after Election Day, too late to be counted, which was 0.09% of the total votes cast there.

What accounts for these extremely low rates of ballots coming in late, despite all the controversies over these deadlines?

Voters were highly engaged, as the turnout rate showed. They were particularly attuned to the risk of delays in the mail from seeing this problem occur in the primaries. Throughout the weeks before the election, voters were consistently returning absentee ballots at higher rates than in previous elections.

The communications efforts of the Biden campaign and the state Democratic parties, whose voters cast most of these absentee votes, got the message across about these state deadlines. Election officials did a good job of communicating these deadlines to voters. In some states, drop boxes that permitted absentee ballots to be returned without using the mail might have helped minimize the number of late arriving ballots, though we don’t have any empirical analysis on that.

In a highly mobilized electorate, it turns out that the specific ballot-return deadlines, and whether they shifted even late in the day, did not lead to large numbers of ballots coming in too late.

That’s a tribute to voters, election officials, grassroots groups – and to the campaigns.