This reporting guide was republished with permission from SciLine, where it first appeared.

Updated June 29, 2026, to reflect the U.S. Supreme Court ruling in Watson v. Republican National Committee that states may continue to count mail ballots received after Election Day.

Voting by mail will play a key role in the 2026 U.S. midterm elections, and not just because a third of voters now cast their ballots that way. With control of Congress at stake, the Trump administration is pushing to restrict mail-in voting, a process, like most electoral issues, traditionally governed by individual states.

For journalists covering the elections, social scientists’ independent research can help them recognize misinformation, avoid errors in reporting about mail ballots, and identify local story ideas.

Here’s why the stakes are high: The percentage of U.S. voters who cast mail ballots during midterm elections tripled to about 32% from 2002 to 2022, according to the MIT Election Data and Science Lab. During the 2024 general election, 29% of voters used mail ballots.

Even before the COVID-19 pandemic became a catalyst, the number had swelled as more states started letting all voters choose to use mail ballots, which, historically, had been restricted to those who could not get to the polls in person on Election Day because of illness, disabilities, work schedules, and other legally specified reasons.

Several factors could have a significant impact on the outcome of elections this fall:

• President Donald Trump issued an executive order in March instructing the U.S. Postal Service not to deliver mail ballots returned by anyone who does not appear on a pre-approved list of eligible voters for each state, a list that would be controlled by his administration. Additionally, operational changes made recently at the Postal Service will delay postmarking for some mail. Election officials in many states check postmarks to determine whether voters sent mail ballots in on time.
• The U.S. Supreme Court on June 29 issued a decision in Watson v. Republican National Committee, a lawsuit that challenged a Mississippi law that allows mail ballots received after Election Day to be counted. In a 5-4 decision, the court ruled that states can continue to count mail ballots that are postmarked by Election Day but arrive later, a practice permitted in 14 states and D.C.
• If voters make an error at any step of the voting process—from completing their ballot and filling out the ballot envelope to mailing it in or submitting it at a designated location—their ballot could be rejected. Election officials in many states will notify voters if there is an issue with their mail ballot and let them correct it. However, most only contact voters when their ballot has not been signed or the signature does not match the one the election office has on file. In swing states such as Pennsylvania, there have been court battles over which of these ballots should be counted.

Advice for journalists

Reporting on mail ballots can be challenging for journalists, partly because state policies on how and when mail ballots must be requested, completed, submitted, collected, verified, and counted vary considerably. Mail ballots also have been the subject of numerous court challenges since partisan focus on the process of voting ramped up following Trump’s defeat in the 2020 election.

Also, journalists frequently have to fact-check common claims about mail ballots. Many people do not fully understand how mail ballots are processed or how differences in policies can affect ballot counts and rejection rates.

And the terminology can be misleading. Though commonly known as “mail ballots” and “mail-in ballots,” these ballots also can be returned in person, with options varying by state.

“Get very acquainted with the facts around mail-in voting because there is a lot of misinformation,” warns Mindy Romero, a political sociologist who is director of the Center for Inclusive Democracy, a research center at the University of Southern California.

For starters, journalists need to know the three types of mail voting and which ones are available in the state or states that they cover. The National Conference of State Legislatures is a reliable source for this information:

• Excuse-required absentee voting: Thirteen states grant requests for mail ballots based on the voter’s reason for not being able to vote in person. States differ in what they consider a valid “excuse,” but many allow voters with disabilities and those who are out of town to use mail ballots.
• No-excuse absentee voting: In 29 states, any voter can request and submit a mail ballot without providing a reason.
• Universal vote-by-mail: Eight states automatically send mail ballots to all active registered voters prior to elections.

Keep in mind that federal law requires all states to let U.S. citizens who live abroad vote by mail in elections for federal offices. The law also mandates that U.S. citizens who are members of the U.S. uniformed services or the Merchant Marine be allowed to vote by mail.

What the evidence shows

Researchers note that policy differences across states make it difficult to gauge whether and how much mail ballots influence voting nationwide. Individual studies tend to focus on one type of mail voting in a limited geographical area, usually a single state, part of a state, or a small group of states.

Research to date suggests:

• Mail ballot fraud is very rare. “Studies consistently have found negligible evidence of fraud in state elections,” researchers write in the 2023 paper from the MIT Election Data and Science Lab. Researchers at the Brookings Institution, a nonpartisan think tank, examined cases of fraud reported during elections in 2016, 2018, 2020 and 2022 and estimated there were about four cases of fraud for every 10 million mail ballots cast, on average.
• Universal vote-by-mail policies do not appear to benefit one political party over another. When researchers examined election data from 1996 to 2018 in three states with universal vote-by-mail policies—California and Washington, which are traditionally Democratic states, and Utah, traditionally a Republican state—they found that the policy “does not appear to tilt turnout toward the Democratic party, nor does it appear to affect election outcomes meaningfully,” they write in a 2020 paper published in the Proceedings of the National Academy of Sciences.
• Ballot tracking boosts voter confidence in elections. Voters in Georgia, Colorado and California who used a free online tool to track their mail ballots during the 2022 midterms reported having higher levels of confidence in elections compared with voters who cast mail ballots in those states but did not use the ballot tracking tool, according to a 2024 analysis from researchers at the Center for Inclusive Democracy at the University of Southern California and the Elections & Voting Information Center at Reed College.
• Mail ballot rejection rates vary across states, as do the reasons election officials reject mail ballots. In 2020, rejection rates ranged from less than 0.5% in states such as Arizona and Florida to 6.4% in Arkansas, finds an analysis the Ash Center for Democratic Governance and Innovation at Harvard Kennedy School released in 2022. More than 40% of ballots that were rejected in Georgia, North Dakota, Tennessee, and Wyoming in 2020 were rejected because they arrived late. Meanwhile, more than 40% of mail ballots that were rejected in Iowa, Nebraska, Maryland and Rhode Island were rejected due to missing signatures.

Avoiding errors in news stories

We consulted three researchers with deep expertise in U.S. elections to create this reporting guide. We also asked them for tips to help journalists avoid some of the most common errors they see in news stories about mail ballots. They shared these three ideas:

1) Remind voters of their options for submitting mail ballots.

Not all ballots delivered to voters by mail are returned by mail. About 40% of the voters who cast mail ballots in 2024 and participated in the 2024 Survey of the Performance of American Elections, a national survey of registered voters conducted after federal elections, said they submitted their mail ballots at designated drop boxes, local election offices, and polling places.

“Reporters will sometimes get that wrong: They will say ‘You have to mail it in,’ but you might not have to mail it,” says Romero, director of the Center for Inclusive Democracy. “Know the different options voters have and include all of those in your stories. Don’t focus on one.”

2) Don’t make broad generalizations about voters who use mail ballots.

“Is there a typical mail voter? The answer is no, that it differs a lot,” says Rachael V. Cobb, an associate professor of political science and legal studies at Suffolk University who serves on Boston’s Election Advisory Committee.

In 2020, MIT scholar Charles Stewart III analyzed the demographics of people who voted by mail during the 2016 presidential election—including race, party identification and family income—in response to growing interest in mail voting amid the COVID-19 pandemic. In a report he wrote to share his results, he points out that the “lack of a major difference between demographic groups is contrary to some claims I have been hearing (and some I believed myself before running the numbers).”

A more recent analysis produced similar findings. However, it notes that Democrats were much more likely than Republicans to cast mail ballots in 2020 and 2022. That difference has since narrowed considerably but still persists, a report the MIT Election Data and Science Lab released last year shows. In 2024, 37%  of Democrats and 24% of Republicans reported voting by mail, compared with 60% of Democrats and 32% of Republicans in 2020.

Prior to 2020, “there was little-to-no partisan difference in voting by mail,” according to the MIT lab.

3) Don’t report or insinuate that ballot rejection rates indicate fraud.

The criteria for rejecting mail ballots varies by state but often include using the wrong envelope, filling it out incorrectly, forgetting to sign the envelope, and submitting the ballot after the state’s deadline.

The most common way election officials verify mail ballots is by comparing the signature on the ballot envelope to the signature they have on file for the voter, according to the National Conference of State Legislatures. Mismatched signatures is one of the most common reasons mail ballots get rejected.

Cobb notes there are many reasons why signatures may not match that have nothing to do with fraud. People’s handwriting often changes over the course of their lives, she explains. Also, as voters age, their fine motor skills tend to decline. As a result, their signatures may become illegible or inconsistent.

News audiences need to understand that, Cobb adds.

“Most people are genuine and just want their ballot cast,” she says.

Researchers share story ideas

Here are three story ideas that journalists can localize for their communities:

The impact of Watson v. Republican National Committee

Romero recommends journalists ask local election officials how they will prepare for elections this fall if the Supreme Court decides that mail ballots received after Election Day cannot be counted.

“You have a lot of mail voters who are used to being able to pop their ballot in the mail on election night or close to it and they know they didn’t have to worry,” Romero says. “If the Supreme Court changes that, will that message get to voters on time? I think it’s highly unlikely.”

Drop box placement

Cobb says the number and location of ballot drop boxes can influence voting, especially for older adults, adults with disabilities, and those who lack transportation.

She suggests journalists examine the issue in their communities. Scientific studies provide important context, including how state policies governing drop boxes can disproportionately affect voters who are racial and ethnic minorities. In some states, drop boxes are prohibited.

Helping voters make sure their ballots count

Cobb stresses the importance of explaining ballot curing—the process of notifying voters about a ballot problem and allowing them to correct it.

“When you go to vote in person, if you mess up on the ballot, the [vote-counting machine] spits it out and you can get another ballot and fix it,” she says, describing  an in-person voting system that uses paper ballots and optical scanners. “But if you vote by mail and make a mistake, you don’t know. So that fail-safe is not immediate. If there is that option [to correct a ballot], people should know about it.”

Bridgett A. King, an associate professor of American politics at the University of Kentucky, urges journalists to ask advocacy organizations about their efforts to educate the public about the process for receiving, completing, and returning a mail-in ballot.

She also advises asking “how advocacy organizations educate the public on the processes that local election offices use to ensure the integrity of [these] ballots.”

Key resources for journalists

These are some of the organizations that provide reliable information and data on mail ballots and U.S. elections.

MIT Election Data and Science Lab: A research center at the Massachusetts Institute of Technology.

Center for Inclusive Democracy: A research center at the University of Southern California.

National Conference of State Legislatures: A bipartisan organization that tracks and reports on various state-level policies and issues.

Ballotpedia: A digital collection of almost 7,000 encyclopedic articles on U.S. politics and elections.

Center for Election Innovation & Research: A nonprofit organization that works with local election officials to build public confidence in elections.

This is a list of the research papers, reports, and experts we consulted for this journalism guide and why we chose them.

Research

Mail voting in the US: Data points to very low fraud and significant benefits to voters
Samara Angel, Jonathan Katz, and Randi Wright. Brookings Institution report, November 2025.

This report from the Brookings Institution, a think tank frequently cited by prominent researchers, features an original and recent analysis of reports of mail ballot fraud.

Voting Outside the Polling Place: Absentee, All-Mail and Other Voting at Home Options
National Conference of State Legislatures report, August 2025.

King recommended this report, parts of which were updated in 2026. It compares and explains state policies on the three types of mail voting.

Vote-by-Mail Ballot Tracking: A Multi-State Analysis of Voter Turnout and Rejection Rates
Mindy Romero, Paul Gronke, Lisa Bryant, Anna Meier, and Michelle M. Shafer. Report from the Center for Inclusive Democracy and the Elections & Voting Information Center, October 2024.

This study, led by Romero, compares the experiences of voters who cast mail ballots and who tracked them using a common ballot tracking tool to those of mail voters who did not track their ballots.

Vote-By-Mail in the United States: Best Practices and New Areas for Research
Paul Gronke, Mindy S. Romero, Enrijeta Shino, and Daniel M. Thompson. MIT Election Data and Science Lab white paper, October 2023.

This paper, which Romero coauthored, offers a detailed look at the research on mail voting and the methodologies different researchers used to conduct their studies.

Ensuring All Votes Count: Reducing Rejected Ballots
Jose Altamirano and Tova Wang. Policy brief from the Ash Center for Democratic Governance and Innovation, August 2022.

Romero recommended this research paper, which examines the most common reasons mail ballots are rejected across the 50 states and District of Columbia.

Universal vote-by-mail has no impact on partisan turnout or vote share
Daniel M. Thompson, Jennifer A. Wub, Jesse Yodera, and Andrew B. Hall. Proceedings of the National Academy of Sciences, June 2020.

This paper, published in a leading scientific journal during the COVID-19 pandemic, investigates whether universal vote-by-mail programs favor one political party over another.

Researchers

We asked political sociologist Mindy Romero to help with this reporting guide because she has studied and written extensively about U.S. elections for many years. We also chose her because of her familiarity with voting issues in California, the nation’s largest state and one of the most recent states to implement a universal vote-by-mail program.

We asked Bridgett A. King to help because of her expertise in certain election-related issues, including felony disenfranchisement, citizen voting experiences, and poll worker demographics. We also chose her because she works in Kentucky, a politically conservative state that employs excuse-required absentee voting.

We asked Rachael V. Cobb to help because she studies and teaches election administration, civic engagement, and political participation and is actively involved in improving elections in Massachusetts, which offers no-excuse absentee voting. Cobb is a member of Boston’s Election Advisory Committee and the board of directors of MassVOTE, a nonpartisan, nonprofit voting rights organization.