Richard H. Pildes is professor of constitutional law at New York University School of Law and is co-author of “The Law of Democracy: Legal Structure of the Political Process.”

As the long lines in recent primary elections show, the desire to vote in person — even during the coronavirus pandemic — remains high. While election officials prepare for unprecedented levels of absentee voting in November, they must also avoid mistakes that undermine the capacity for in-person voting. Indeed, as long as in-person voting can be made reasonably safe and efficient, we should take every step to assure voters they have an in-person voting option — and to encourage them to use it. Failing to do so could lead to major problems.

Tasking election officials with preparing for high levels of absentee voting, while also ensuring capacity for strong in-person voting, is a tall order. They will be tempted to push people into the absentee process and to underinvest in in-person voting, as has happened in several primaries over the last few weeks. Yet, four reasons make in-person voting even more essential this fall.

First, precisely because levels of absentee voting will be so high, that process will face tremendous logistical pressure. Moreover, all states — as well as the U.S. Postal Service — will be experiencing this surge simultaneously. Even with recent, lower-turnout primary elections in individual states, we have witnessed the strains this puts on a system struggling to convert, virtually overnight, into voting by mail. Requested absentee ballots do not arrive; others are not returned until too late to be counted. In a close election, such logistical and administrative failings could become explosive. Voting in person, whether early or on Election Day, will relieve pressure on the absentee process — and be a critical fallback option as problems arise.

Second, absentee ballots are more complex to process and are rejected at much higher rates than ballots cast in person (3 to 10 percent in recent elections). Voters must remember to sign their name on the ballot envelope; in some states, that signature must be witnessed or notarized. Processing these ballots is also more difficult. Officials must determine whether the signature on the ballot envelope matches the voter’s registration file and whether the ballot complies with other procedural requirements.

Voters who make a mistake on their ballot envelope should be given an opportunity to fix it. Though a low rejection rate might be tolerable when a small share of the vote is cast by absentee ballots, it is not when half to three-fourths of votes are cast this way. Yet correcting those mistakes adds more delay and increases the burdens on the system. When voting in person, mistakes can often be corrected on site; optical-scan machines will immediately tell a voter whether they have accidentally voted twice in the same race.

Third, a significant percentage of voters — historically, minority communities and younger voters; more recently, Republicans — simply do not trust that their votes will be counted fairly if mailed in.

All this is prelude, however, to the final and most important reason in-person voting should be encouraged. Even if absentee voting proceeds smoothly, a massive surge in mail-in ballots means hundreds of thousands of votes will not be counted until days after Election Day. Two weeks after its June 2 primaries, Pennsylvania was still counting absentee ballots. That experience creates one of the greatest risks to ensuring an election outcome widely accepted as legitimate this fall. If one candidate is ahead in key states on the night of the election, but loses those leads — and the race — over the course of the following week, charges of a stolen election will inevitably erupt.

To protect the capacity for in-person voting and also make it safe, here are a few suggestions: One-third of people vote at schools, yet many schools are, understandably, banning outsiders this fall. All states should make Election Day a school holiday, which would also enable teachers and staff to serve as poll workers. To replace locations likely to be unavailable, such as firehouses or senior centers, venues such as big-box retail stores can be turned into polling places. To substitute for the large share of poll workers who are seniors, we need a major effort to recruit poll workers from the ranks of students and others less vulnerable to covid-19 infection. Poll workers must be provided with the necessary equipment to protect themselves and continuously sanitize polling places. Early voting opportunities should be expanded.

If Congress’s contribution is focused on providing funding to enable in-person voting, bipartisan support might be possible. In Kentucky, a coalition of Republican legislators and minority voters sued, unsuccessfully, to force the state to open more in-person sites. Most importantly, election officials, as well as campaigns, must not suggest that absentee voting is the only safe way to vote; that will not only deluge the absentee process but also depress turnout among groups who only trust voting in person.

The more people who vote in person, the sooner the result will be known, the less the risk that the absentee process will collapse, and the lower the threat that the election will melt down. We must not lose sight of that danger, even as states rightly ramp up the absentee part of the election.

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