Before the pandemic, there wasn't any difference in the rates at which Democratic and Republican voters actually cast their ballots by mail or in-person. That may change now.
Based on nationally representative surveys conducted in the spring of 2020 and through the summer, researchers report a significantly greater preference for mail, or absentee, ballots among Democrats than among Republicans. The researchers document for the first time a partisan gap in stated preferences in April 2020. By June, that gap had doubled - from a 10% difference in April to a 20% one in June. The gap was even wider among those exposed to scientific projections about the COVID-19 pandemic, with Democrats then expressing even greater preferences for mail ballots while Republicans were unaffected.
These findings are detailed in a study published in the Proceedings of the National Academy of Sciences.
After finalizing their PNAS paper, the research team - members of the New Electorate Project from UC San Diego, UC Riverside and the University of Southern California - continued to survey America's eligible voters. The partisan gap, they say, has continued to grow: By late August, more than half of Democrats but less than a quarter of Republicans said they personally 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 UC San Diego professor of political science, who is senior author on the PNAS study and the New Electorate Project's principal investigator.
Study also finds widespread, bipartisan support for mail ballots
An encouraging finding: Personal preferences aside, there is bipartisan support for making mail ballots available to all voters who want them.
"Despite the polarization, we see support across the board for making voting more accessible," said Mackenzie Lockhart, corresponding author on the PNAS study and a political science doctoral candidate at UC San Diego.
"In all our surveys, a majority of Republicans and Democrats supported not only making vote-by-mail ballots available to anyone who wants them," Lockhart said, "but also sending ballots directly to every registered voter, regardless of how they intend to vote."
Kousser notes that policies allowing any voter who requests an absentee ballot to cast their vote this way are place in most states, including nearly every swing state in the presidential election.
Why the gap?
The researchers attribute the growth in the partisan divide to two things: signals from partisan elites in both parties and Republican partisans' distrust in science and experts.
"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."
Will the gap matter in November?
Each of the surveys was conducted with more than 5,600 Americans of voting age. What remains an open question is whether there will now also be a partisan difference in actual voting behaviors, with Republicans turning out to vote in person at polling places at greater rates than Democrats. And will Democrats, in turn, vote at greater rates by mail ballot - which, depending on state laws, they'll then drop off at polling places or secure drop-boxes, or send through the mail?
Also an open question: Will this gap affect the outcomes of the 2020 U.S. presidential election?
"We don't know what will happen in November," Lockhart said, "and if things go smoothly with both voting methods, then the partisan differences we found might not matter. 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."
If a spike in infection rates makes voting in-person more difficult or delays in the mail mean mail ballots arrive after the deadline, Lockhart said, how exactly partisans decide to vote could have a big effect on the election.
The study's other co-authors are Seth Hill of UC San Diego, Jennifer Merolla of UC Riverside and Mindy Romero of the University of Southern California
The New Electorate Project is funded by the UC Office of the President.