In light of dangers posed by coronavirus, some have suggested vote-by-mail as an alternative to in-person polling.
But some policymakers argue mail ballots would give one party an advantage.
A new study in the journal PNAS tests that notion.
To gauge the effects of sending a ballot to every registered voter while reducing in-person voting options, researchers looked at presidential, senatorial and gubernatorial general elections in California, Utah and Washington state between 1996 and 2018.
Comparing counties that adopted vote-by-mail to those that didn't, they found vote-by-mail slightly increased overall voter turnout but did not favor Democrats or Republicans in turnout or share of votes.
