There are 136 pledged delegates at stake in Ohio when the crucial midwestern general election battleground state holds Democratic presidential primary elections on Tuesday, along Florida, Illinois and Arizona.

Ohio allows for open primaries, meaning a voter doesn’t have to register with a particular political party to vote in its primary. Voters select the ballot of the party whose primary they wish to vote in when they arrive at the polling location. Ohio does allow early voting.

THE LATEST FROM FOX NEWS ON THE 2020 PRESIDENTIAL CAMPAIGN

Polls on presidential primary day in the Buckeye State open at 6:30 a.m. ET and close at 7:30 p.m. ET.

Here’s a look at recent past winners.

2016

DEMOCRATS

Hillary Clinton - 57 percent

Bernie Sanders - 43 percent

REPUBLICANS

John Kasich - 47 percent

Donald Trump - 36 percent

Ted Cruz - 13 percent

Marco Rubio - 3 percent

2012

REPUBLICANS

Mitt Romney - 38 percent

Rick Santorum - 37 percent

Newt Gingrich - 15 percent

Ron Paul - 9 percent

2008

DEMOCRATS

Hillary Clinton - 54 percent

Barack Obama - 44 percent

John Edwards - 2 percent

REPUBLICANS

John McCain - 60 percent

Mike Huckabee - 31 percent

Ron Paul - 5 percent

Mitt Romney - 3 percent