UCSD researchers find a widening party-line gap over mail-in voting, partly because of COVID-19

Stock photo of a mail-in ballot
UC San Diego-led research found a growing partisan divide on the issue of voting by mail.

Voters are more likely than ever to be split along party lines on the issue of mail-in voting, partly due to COVID-19, according to a report by a UC San Diego-led political science research team.

According to the report, written by the New Electorate Project and published Sept. 22, there was no difference before the pandemic in the rates at which Democratic and Republican voters cast their ballots by mail or in person.

However, based on nationally representative surveys conducted this spring and summer, researchers reported a significantly greater preference for mail-in ballots among Democrats than Republicans. Each survey was conducted with more than 5,600 Americans of voting age.

The researchers documented a partisan gap in stated preferences for the first time in April. By June, the gap had doubled, from 10 percent to 20 percent.

The gap was even wider among those exposed to scientific projections about the COVID-19 pandemic, with Democrats expressing even greater preference for mail ballots while Republicans were unaffected.

The findings are published in the Proceedings of the National Academy of Sciences.

After finalizing the paper, the team — which includes researchers from UC San Diego, UC Riverside and USC — continued to survey America’s eligible voters. The partisan gap has continued to grow, the researchers say. By late August, more than half of Democrats but less than a quarter of Republicans said they preferred to vote by mail.

“A serious partisan divide has opened up on preferences for voting by mail and has grown from a gap to a gulf over the past several months,” said Thad Kousser, a UCSD political science professor, senior author of the study and the New Electorate Project’s principal investigator.

Personal preferences aside, there is bipartisan support for making mail ballots available to all voters who want them, according to the research.

“Despite the polarization, we see support across the board for making voting more accessible,” said Mackenzie Lockhart, lead author on the study and a political science doctoral candidate at UCSD. “In all our surveys, a majority of Republicans and Democrats supported not only making vote-by-mail ballots available to anyone who wants them but also sending ballots directly to every registered voter, regardless of how they intend to vote.”

The researchers attribute the growth in the partisan divide to two things.

“Republican and Democratic lawmakers have staked out very different positions on voting by mail, and voters have begun to notice,” Lockhart said.

“But on top of that, our evidence suggests that voters’ views on COVID-19 are probably also polarizing the issue. We found that scientific predictions about the COVID-19 pandemic had much smaller effects on Republicans than Democrats and contributed to a larger gap between partisans.”

It remains an open question whether the gap will affect the outcome of the 2020 presidential election.

“We don’t know what will happen in November, and if things go smoothly with both voting methods, then the partisan differences we found might not matter,” Lockhart said. “But based on our results, if either mode of voting — in person or by mail — ends up not running smoothly, that’s when these differences in how partisans want to vote could matter.”

Lockhart said potential complications could include a spike in COVID-19 infection rates making voting in person more difficult, or delays in the mail leading to those ballots arriving after the deadline. ◆