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Mail voters who are informed and have opportunities to fix ballot errors ahead of elections are much more likely to have their votes counted, a new study of the 2024 election in Pennsylvania has found.
The study, from the University of Pennsylvania, provides hard evidence to back up the arguments that county officials have used for years to justify such “notice and cure” policies for defective mail ballots.
“Vote curing policies help balance the tension between promoting both access and integrity in mail balloting,” the study’s authors wrote. “In short, vote curing can reduce the number of eligible voters whose deficient mail ballots become ‘lost votes.’”
Mail ballots can be rejected for a variety of reasons, including lacking a signature on the outer envelope or lacking the inner secrecy envelope. In some elections, ballots have also been rejected for lacking a date on the outer envelope, although this requirement is currently being litigated in state and federal court.
Pennsylvania counties have a wide array of methods for letting voters fix these errors. Some ask voters to fix the errors in person at the county election office — for example, by adding a missing signature — while others automatically return deficient ballots to voters, or cancel deficient ballots and reissue new ones. Other counties only allow voters to correct the error by casting a provisional ballot at their polling place on Election Day.
The study examined how many voters corrected their deficient mail ballots across counties that use these different methods and found that voters were 25 percentage points more likely to have their vote counted if they were told of a disqualifying error before Election Day, and 10 points more likely to have their vote counted if they had an opportunity to correct that error before Election Day, rather than just on Election Day.
The study also found that when deficient ballots were automatically returned or replaced, allowing voters to make a correction by mail, voters were 25 points more likely to have their vote counted.
Jim Allen, the election director of Delaware County, one of the counties that automatically replaces deficient ballots, said this method roughly doubled the rate at which voters were able to cure their ballots.
“Also, it reduced traffic at our Voter Service Center and reduced provisional ballots,” he said via email.
Likewise, counties have a variety of methods for notifying voters of deficiencies with their mail ballots, including calls, emails, and publishing lists online. The study measured if a voter was notified by looking at when their ballot was recorded as deficient in the state public ballot tracking system, where voters or political parties could see the issue and which also automatically emails voters if there is an error with their ballot.
But providing an email is optional when applying for a mail ballot. According to data from the just-concluded 2026 primary election, roughly 20% of mail ballot requestors didn’t provide an email address. For those voters, what happens next depends on what county they live in. Some may not be notified at all that their ballot may be rejected.
The mail ballot application says the email “may be used to contact you about important information" but not expressly that it could be used to notify voters of errors with their mail ballots that may disqualify their vote.
Michael Morse, a law professor at the University of Pennsylvania and one of the study’s coauthors, said that more explicit language on the application could lead to more voters providing their email address and, therefore, getting notified if their ballot is at risk of rejection. He also suggested that the state could use email addresses they may have for the voter in other databases, such as the state’s voter rolls.
The Pennsylvania Department of State said in a statement that it encourages voters to fill out the email section, and that it was reviewing the study and “is always open to considering ways to improve communication with voters.”
The study also highlights the equal protection principle, which could be the next frontier in legal fights over Pennsylvania’s mail ballot curing rules.
In a case from the 2000 election, Bush v. Gore, the U.S. Supreme Court found that Florida’s recount of that year’s presidential election violated the 14th Amendment’s equal protection clause because counties were using inconsistent standards to decide which ballots counted.
Pennsylvania’s system, in which voters across the street from each other might have vastly different opportunities to cure their ballots based on what county they live in, could also test this principle. The argument has been made in cases before, Morse noted, but hasn’t yet been fully litigated in Pennsylvania.
Morse said when and how the equal protection principle applies in the context of election administration is unclear, since the decentralized nature of elections means there will always be variation across counties, and they can’t all violate the principle.
“That fight really hasn't developed much … [because] it hasn't mattered yet to the Pennsylvania outcome,” he said. “The only reason it was going to come up in 2024 is if the number of deficient mail ballots was within the margin of victory, and it wasn't.”
The equal protection question may not have had much of a bearing on Pennsylvania’s curing policies yet, but in other states it has. A recent decision in a case in North Carolina found that the state’s cure process violated the equal protection principle for some voters.
Carter Walker is a reporter for Votebeat in partnership with Spotlight PA. Contact Carter at cwalker@votebeat.org.