Mail-in voting has no partisan advantage, Stanford researchers say

Mail-in and absentee ballots improve voter turnout and make elections more democratic, but the argument that one political party would have an advantage over another in a mail-in ballot election doesn’t appear credible, studies by multiple Stanford University researchers have found.

Implementing a broad mail-in ballot program could have some potential pitfalls in the November election, however, for states and counties when putting together the necessary infrastructure for distributing and sorting the ballots and ensuring that all of the votes are counted, they said.

In one study, Stanford political scientists Adam Bonica, an associate professor, and Hakeem Jefferson, an assistant professor, both of the Department of Political Science, analyzed election results in Colorado, one of the few states that conducts its elections completely by mail. Voter turnout increased about 9.4% after the program was rolled out in 2013, according to a working paper they co-authored, which studied data from five elections between 2010 and 2018. That percentage was even higher among people ages 30 and younger, where they found voter turnout increased by 15%.

Turnout was also high for blue-collar workers, voters without a high school diploma, those with less wealth and people of color, the researchers found.

“These findings suggest that making it easier to vote increases electoral participation among those who may otherwise remain unengaged,” they wrote.

Bonica and Jefferson did not find that Colorado’s all-mail voting disproportionately benefited either the Republican or Democratic parties, but turnout among Independents was nearly 12% higher than in previous elections, the researchers said.

“Colorado’s experience demonstrates that all-mail voting is not only safer than in-person voting but also better for democratic representation, with all age, income, race, occupational and education groups benefiting from its introduction,” according to the working paper.

To address rapid changes for this November’s election, the researchers suggested states and counties should offer in-person voting options with safety measures to avoid duplicative voting and allow people who miss the deadline to receive a mail-in or absentee ballot a chance to head to the polls.

Another Stanford study by Andrew Hall, a political science professor, examined data from California, Utah and Washington, three states that have gradually expanded their vote-by-mail programs. Mail-in and absentee voting did not affect overall turnout for either Republicans or Democrats, and mail-in voting didn’t affect the share of votes that went to Democratic candidates. Mail-in voting did increase turnout by about 2% on average, Hall and his team found.

“Our paper has a clear takeaway: claims that vote-by-mail fundamentally advantages one party over the other appear overblown,” the researchers wrote.

Hall is also continuing a study of absentee voting, which includes analysis of a primary election held during the COVID-19 pandemic. Overall, his findings so far are consistent with the earlier study. But holding an election during the pandemic poses unprecedented challenges, and it’s difficult to predict exactly what will happen in November, he said in an interview with Stanford News Service.

“Vote-by-mail is an extremely helpful part of the overall, nonpartisan election toolkit, but it is not a panacea. Voters should consider their local context, including prospects for logistical issues with vote-by-mail and the safety precautions their local officials are implementing to support in-person voting before deciding how they want to vote,” he said.

Nathaniel Persily, a Stanford researcher and law professor, said he has concerns about ensuring that all mail-in ballots are counted.

“In such a short period of time it is very difficult for states to adapt to this new environment and it requires changes at every step in the administration of the election, from the beginning of registering votes to the end of counting their votes,” Persily, former senior research director of the Presidential Commission on Election Administration, told Stanford News Service. He is co-leading research with Charles Stewart III of the Massachusetts Institute of Technology through the Healthy Elections Project.

In Florida’s primary election earlier this year, Persily and Stewart found that mail-in ballots cast by African Americans, Latinos, first-time voters and young people were significantly less likely to be counted because the ballot was received late, signatures were missing or they did not match the signature on file.

“That’s a real concern as we approach the (general) election,” Persily said.

States would also need to develop infrastructure such as mail-in ballots, sorters and scanners to meet the increased demand, he said during an interview with Stanford Legal.

Americans must prepare to vote in a different way this year, he said.

“We need to start treating this election like we would a natural disaster, like a hurricane or earthquake. We need to mobilize around all levels of government and civil society and that includes Congress appropriating more money and it includes massive efforts about educating people about how to vote safely and we need people to volunteer,” he said.

To help voters and election officials, the Healthy Elections Project has prepared a vote-by-mail resource guide, which includes tips on signature verification and vote tallying.