As of today, residents of 31 states have started early voting for the Nov. 4 midterm elections.

A total of 36 states, plus the District of Columbia, allow voters to cast their ballots early in person. Minnesota has the longest period of early voting — from mid-September all the way through Election Day — while 14 states don’t open the polls early at all.

Election administrators have said that early voting reduces wait times for voters and gives poll workers time to resolve glitches in the system. As a result, more voters have started to turn out early, according to federal election data. The policies help voters in particular who are low-income and struggle to take time off work to get to the polls.

Since the 2012 elections, four battleground states have passed laws to limit the days on which you can vote early, including Ohio.

Ohio’s law, passed in 2014, removed one week of early voting, during which voters could register to vote and cast a ballot on the same day. Then, Secretary of State John Husted issued a directive eliminating early voting during the evenings, all Sundays and the Monday before Election Day. Husted said the cuts would preserve “uniformity,” so that voters across all counties would have to vote during the same hours.

The ACLU filed suit against both Ohio policies, charging they discriminated against low-income voters, who are disproportionately African American, who aren’t able to take time off work to get to the polls. In September, the Supreme Court allowed the cuts to stand; *Ohio then issued a new directive allowing voters to cast ballots from 1-5 p.m. on the Sunday before Election Day, and the following Monday until 2 p.m.

Find out more in our vote-tracking project, Ballot Watch. See which states are already voting below. [Note: This post has been updated to accurately reflect the most recent changes to Ohio’s early voting policy.]

Chris Amico, Former Interactive Editor

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FrontlineEditors@wgbh.org

Sarah Childress, Former Series Senior Editor, FRONTLINE