More than 540,000 mail ballots were rejected during primaries across 23 states this year - nearly a quarter in key battlegrounds for the fall - illustrating how missed delivery deadlines, inadvertent mistakes and uneven enforcement of the rules could disenfranchise voters and affect the outcome of the presidential election.
The rates of rejection, which in some states exceeded those of other recent elections, could make a difference in the fall if the White House contest is decided by a close margin, as it was in 2016, when Donald Trump won Michigan, Pennsylvania and Wisconsin by roughly 80,000 votes.
This year, according to a tally by The Washington Post, election officials in those three states tossed out more than 60,480 ballots just during primaries, which saw significantly lower voter turnout than what is expected in the general election. The rejection figures include ballots that arrived too late to be counted or were invalidated for another reason, including voter error.
The stakes are high as the most chaotic presidential election in memory collides with a pandemic, which has led 20 states to expand or ease access to voting by mail as a public health measure.
Election experts said that the combination of the hotly contested White House race and millions of first-time mail voters could lead to a record number of ballot rejections and trigger a searing legal war over which are valid - and who is the ultimate victor.
"If the election is close, it doesn't matter how well it was run - it will be a mess," said Charles Stewart, a political science professor at MIT who studies election data.
"The two campaigns will be arguing over nonconforming ballots, which is going to run up against voters' beliefs in fair play," he said.
President Trump has already cast doubt on whether he will accept a loss to Democratic nominee Joe Biden, and has repeatedly stoked unfounded fears about voting by mail. Top campaign advisers are also mapping out a post-election strategy centered in part on challenging mail ballots that do not have postmarks, as The Post previously reported.
Citing news coverage of rejected ballots last month, Trump called the situation "a mess" and predicted that the presidential race will be the "most rigged election in history."
For Democrats and voting rights advocates, rejected ballots are a serious concern because they raise the potential for many people to be disenfranchised - not because they reflect widespread corruption or election tampering.
Both sides agree that the race for the White House could come down to a fight over which mail ballots are counted.
Democratic lawyers and election officials in more than three dozen states are now pushing to limit the reasons a ballot can be rejected, which studies have found tend to disproportionately invalidate ballots from younger voters and voters of color. Recent mail backlogs at the U.S. Postal Service have put additional weight behind efforts to count ballots that are postmarked by Election Day but arrive late, among the most common reason for rejections. While some states have changed their rules, others have not or are stuck in litigation.
The number of mail ballots rejected in 23 states in this year's primaries outstrips the nearly 319,000 mail and absentee ballots that were thrown out nationwide in the 2016 general election. The number of tossed ballots four years ago amounted to 1% of the roughly 33.4 million mail ballots cast that fall, according to data from the U.S. Election Assistance Commission.
About 195 million Americans are now eligible to cast ballots by mail for the Nov. 3 election - at least 83% of voters, according to a Post tracker. Some states are poised to begin sending voters mail ballots for the fall elections as soon as next month.
But the ease of casting a ballot from home also means more opportunities for people to make mistakes in filling out the forms, or for mail problems to delay the ballots' return to election officials.
"Any time you see a dramatic increase in participation in any kind of voting, what you also see come along with that is folks who are maybe new to that process, who aren't incredibly clear on the rules," said New Mexico Secretary of State Maggie Toulouse Oliver, a Democrat and president of the National Association of Secretaries of State.
The shift toward mail voting is also testing election systems across the country, magnifying antiquated state rules about ballot rejection and the lack of a process in many jurisdictions for voters to fix problems with their ballots.
Studies have found that votes cast by mail, a process that involves several steps and more opportunity for error, are more likely to be rejected than those cast in person at polling locations.
This year, voting in New York emerged as a cautionary tale after problems with absentee ballots plunged two congressional races into chaos for six weeks before winners were declared. In the 12th Congressional District, Rep. Carolyn Maloney, a Democrat, defeated two-time challenger Suraj Patel by about 3,700 votes; roughly 13,000 ballots were declared invalid in the race, many with missing or late postmarks.
The record use of mail balloting this year has meant that many Americans are grappling for the first time with the idea that their vote did not count.
Among them was Philadelphia resident Stephanie Fusco, 26, who got a notice in June that the ballot she cast in Pennsylvania's presidential primary that month for Sen. Bernie Sanders, I-Vt., was rejected. The reason given: election workers "could not obtain" her required signature from the ballot.
"I was absolutely irate when it happened," said Fusco, who worked as a medical technologist until she was furloughed because of the pandemic. "I did everything well before the deadline, and I know that I signed it. I signed it on the little box on the envelope."
The Post found that 540,026 ballots were disqualified in 23 states in the 2020 primary season; a similar analysis by NPR tracked 558,032 ballots that were rejected in 30 states. A large share of the rejected ballots tracked by The Post were in two jurisdictions: California, which threw out more than 102,000, and New York City, which tossed more than 84,000.
In eight battleground states, more than 125,100 ballots were rejected by election officials in this year's primaries, according to data compiled by The Post. The states were Florida, Maine, Michigan, Nevada, North Carolina, Ohio, Pennsylvania and Wisconsin.
The Post totals include the number of ballots rejected in a primary held in each state this year, including several that took place before the novel coronavirus emerged as a serious concern in the United States. The figures almost certainly understate the number of rejections for several reasons, including failures by some counties to report their data.
Among the battleground states, rates of rejection ranged from 10% on March 3 in Maine, where many ballots arrived too late to be counted, to less than 1% in Florida and Michigan this month, according to The Post's analysis.
Maine is now considering installing ballot drop boxes in each town to help avoid potential mail delivery problems in the fall.
Testifying Friday before a Senate panel, Postmaster General Louis DeJoy called the swift handling of election mail his "sacred duty" and promised that ballots would be delivered in time for counting across the country.
"The Postal Service will deliver every ballot and process every ballot in time that it receives," he said.
Michigan Secretary of State Jocelyn Benson, a Democrat, predicted that the number of rejected ballots in her state could double in November compared to this month's primary, when 10,694 votes were disqualified. Trump won Michigan by 10,704 votes in 2016.
About 6,400 of the ballots thrown out this month arrived by mail after Election Day, the state's deadline for receipt, amid reports of Postal Service backlogs in the state.
Benson has called on the legislature to amend the law to allow such votes to count in November if they are postmarked by Election Day, even if they arrive up to two days later.
"If that doesn't change and if there are no other changes, we're facing a scenario where we could have to reject a number of otherwise valid votes sent through the mail that are delayed through no fault of the voter, because of the Postal Service or some other snafu," she said last week on a call with voting rights activists. "So those voters could be disenfranchised, and that number could exceed the margin of victory for a number of races, statewide and local."
Trump has criticized Benson, accusing her of creating opportunities for voter fraud by sending absentee ballot applications to all registered voters before the primary.
Benson said she anticipates "significant challenges, particularly in Michigan, to the result of the election and the sanctity of the process" in November.
"We're prepared to fight to ensure the public can have confidence that the results for our elections, whatever they may be, are an accurate reflection of the will of the people," she said.
The possibility that millions of Americans could be voting by mail for the first time probably will exacerbate confusion this year.
Daniel Smith, a political science professor at the University of Florida, has found that Floridians who cast ballots in person in the 2016 and 2018 general elections were twice as likely to have their mail ballots rejected in the 2020 presidential primaries than those who voted by mail in the two prior contests.
"Experience matters," he said of the mail voting process. "So we can apply that across the country - if you lack experience voting by mail, the odds of you casting a ballot that doesn't count will go up."
"We're going to see those [rejection] rates skyrocket even more" in November, he said.
Smith's research also found that ballot rejections can disproportionately affect younger voters and voters of color.
In Florida, where mail ballots were rejected at a rate of a little more than 1% in the 2016 and 2018 general elections, the rate of rejection for ballots cast by 18- to 21-year-olds was more than eight times greater than for voters older than 65, he said. Similarly, the absentee ballots of Black and Hispanic voters were more than twice as likely to be rejected as those of White voters, his research shows.
Such disparities exist across the country. In Michigan, Benson noted recently that Black, Brown and Asian American communities in the state see higher rates of ballot rejection.
"We need to educate about how to ensure that those votes are counted," she said.
Reasons for rejection vary. The failure to provide a signature or to return the ballot on time tend to be the most common problems, according to state data.
"A lot of people don't follow instructions," said Gerry Cohen, a member of the Wake County Board of Elections in North Carolina, which reviews every problematic ballot to determine whether it is valid.
In this year's primary, "one voter sent in his ballot and it was rejected because he hadn't signed it at all," he said. "We sent a new ballot the next business day. He returned his new ballot four days later and didn't sign it either."
Voters are often not familiar with all the rules for completing mail ballots - or the unintentional errors that can disqualify them, such as a stray mark by a voter's pen. In Kentucky, tearing off a perforated flap on the inner ballot envelope means your vote won't count. In Wisconsin, a tiny tear in the envelope itself can invalidate the ballot, even if it is repaired by tape.
Stewart said many rules stem from 19th-century concerns about vote-buying and other types of fraud.
Some states add another layer of protection against voter fraud by requiring that the signature on the ballot envelope match the voter's signature on file with the government. While the practice is widely accepted and employed by states such as Colorado and Washington that offer universal mail voting, lawsuits have claimed that uneven training and enforcement in some jurisdictions can lead to false ballot rejections.
In at least 20 states, voters must be notified and given the chance to fix or "cure" signature problems that could invalidate their ballots. But the rules vary in the rest of the country, and some voters are never told that their ballots did not count.
Requiring ballots returned through the mail to carry a postmark with the date is another safeguard, used to prevent ballots from being counted after the deadline. But the Postal Service is not required to postmark every piece of mail, creating problems for election officials who receive ballots without an official date stamp.
Democrats and voting rights groups are now waging court battles to ensure that absentee ballots are not discarded on technicalities, pushing to require that ballots postmarked by Election Day be counted and to make signature-matching laws more voter-friendly. In response to litigation, Minnesota and Pennsylvania agreed this month to count ballots postmarked by Election Day and received within a certain window. And in Indiana, a federal judge ruled that election officials cannot reject ballots for dissimilar signatures without notifying voters.
Republicans have countered with their own litigation, arguing that strict signature-matching rules and voter identification requirements are necessary to prevent fraud. They have opposed Election Day postmark rules, claiming they result in invalid, late-cast ballots being counted.
"Overhauling the way Americans vote less than 80 days out will only spread chaos and confusion," Republican National Committee spokeswoman Mandi Merritt said in a statement.
States are trying to keep rejection numbers down in a variety of ways: public education campaigns encouraging voters to return their ballots early; pressure on DeJoy, as well as additional coordination with postal officials; new ballot drop boxes; online ballot tracking; redesigned ballots; and streamlined ballot instructions.
In Wisconsin, election officials are offering options for voters to return their ballots by mail or in person, depending on their comfort level, said Reid Magney, spokesman for the state election commission.
The state has added mail bar codes this year through which voters can track the ballot as it is delivered and sent back to the clerk to be counted.
There is also a major voter education effort underway to teach voters how they can cast absentee ballots, including through a series of two-minute videos online.
"Time is our friend with all of this," Magney said. "Our hope is that by getting people to act early, that's going to be a big help."
Other states have adopted new policies.
This month, the Virginia Board of Elections approved a regulation allowing absentee ballots to be counted even if the postmark is missing or defective. Ballots returned by mail in the state must arrive by noon Nov. 6 to count.
A similar rule drew a legal challenge this month from the Trump campaign and the RNC after it was enacted in Nevada.
North Carolina in May loosened its witness requirement for absentee ballots during the pandemic, allowing ballots to count if they are signed by one witness instead of two or a notary.
Still, Allison Riggs, interim executive director of the Southern Coalition for Social Justice, called the bill a "Band-Aid over a gushing arterial wound." The group filed suit and won a ruling Aug. 4 that the state must provide a cure process to help voters fix mistakes that otherwise would lead to their ballots being rejected.
Riggs estimated that if voter participation rates are similar to 2016, about 115,000 ballots will be saved by the ruling.
While North Carolina is among the roughly 30 states without a signature-match requirement, roughly 25 ballots were still rejected during the primary under the code "signature different," Riggs noted. Another roughly 1,700 ballots were coded as spoiled, with the specific reason unclear.
"It's pretty troubling," Riggs said. "If North Carolina poll workers and election workers aren't really clear on the rules and how to apply them and there isn't a lot of standardized guidance, that handful of essentially discrepancies - that can turn into some big numbers come November."
For voters who learned that their ballots were tossed this year, the experience was deeply demoralizing, shaking their faith in the system.
Fusco, the Philadelphia voter who tried to vote for Sanders, said that when she heard her ballot was rejected, she tried to call the elections office but got no answer.
Finally, Fusco received a reply by email from a city official who said she failed to sign her name on the ballot envelope, according to messages reviewed by The Post. After Fusco insisted this was wrong, the official said she had signed, but the signature was only her initials, whereas the signature on her voter registration record was her full name.
"I've been using my initials as my signature for the past several years," she said. "We bought a house and that is my signature. It's on my license. It's how I've been signing my name for years. My registration record is probably from when I was 18. . . . I don't know how you can expect signatures to stay the same for so many years."
"Making this process so painstakingly difficult is a form of voter suppression," she wrote in a reply to the official.
Philadelphia officials said 3.8% of ballots cast by mail for the June primary were rejected. "The Board [of Elections] makes every effort to accept every ballot they can in accordance with the law," the city's deputy commissioner, Nick Custodio, told The Post in an email. "Voters have the opportunity [to] appeal individual decisions directly to the Board itself."
Fusco, now working as a freelance illustrator, said she was uncomfortable making a formal appeal during the pandemic because she feared it would require attending an in-person meeting. But now, she said, she feels compelled to cast a ballot in person in November to ensure that it counts.
"I have no idea what that is going to look like," she said. "It's scary. It's almost like, even if I do go vote in person, is it going to matter? Even if I do put myself at risk, is it going to matter?"
The Washington Post’s Michelle Ye Hee Lee, Antonio Olivo and Jada Yuan contributed to this report.