Derrin Robinson has worked in Oregon elections for more than 30 years, long enough to remember when voters in the state cast their ballots at physical polling sites instead of by mail.

As the nonpartisan clerk of Harney County, a vast, rural expanse larger than Massachusetts, Robinson oversees elections with about 6,000 registered voters. Oregon has exclusively conducted elections by mail since 2000, a system he thinks works well, requires fewer staff and doesn’t force voters to travel through treacherous weather to reach a polling place.

“As you can tell, I’m not an advocate for going back,” Robinson said.

Not everyone agrees. An Oregon Republican lawmaker has introduced legislation to end the state’s mail voting law, and organizers of a ballot measure campaign seeking to ban mail-in voting say they have gathered thousands of signatures.

Across the United States, voting by mail faces a moment of uncertainty ahead of the midterm elections next year.

President Donald Trump has assailed mail-in voting and vowed this summer to lead a movement to eliminate the practice, promoting baseless claims that mailed ballots are linked to widespread fraud. Some states are also reevaluating their mail-in voting laws, including shortening or ending grace periods that now require election officials to count mailed ballots that arrive after Election Day.

The U.S. Supreme Court in November agreed to take a case that could end ballot grace periods nationwide. A decision by the justices late next spring or early summer striking them down could affect 16 states and the District of Columbia, potentially upending the rules of elections as states prepare to hold primaries ahead of the November midterm elections that will determine control of Congress.

Mail-in voting surged in 2020 amid the COVID-19 pandemic, when 43% of voters cast their votes by mail. The percentage of voters mailing their ballots has fallen from that peak but remains above pre-pandemic levels. About 30% of voters cast mail ballots in 2024, according to data gathered by the U.S. Election Assistance Commission.

That’s 46.8 million voters, underscoring the electoral and political stakes involved in any major change to mail-in voting.

“THE MAIL-IN BALLOT HOAX, USING VOTING MACHINES THAT ARE A COMPLETE AND TOTAL DISASTER, MUST END, NOW!!!” Trump posted in August on his social media site, Truth Social.