Washington (CNN) Ohio voters approved a gerrymandering reform proposal Tuesday that would change how the state draws congressional district lines following the next US Census.

The Issue 1 ballot measure passed 75% to 25%, based on unofficial results from the Ohio secretary of state's office. It will be implemented in 2021.

Ohio's population size in 2020 US Census results will determine the number of seats the state will have in the US House of Representatives. Once the number of seats is determined, the lines will be determined by the state legislature. Then, in order to adopt the map for 10 years, 60% of Ohio state legislators and 50% of members of the two leading parties (likely Republicans and Democrats) must approve it. If it's not approved, a commission that includes the governor, auditor, Ohio's secretary of state and four lawmakers will move to approve or decline the redistricting proposal.

If that commission fails to approve the new map, it would be sent back to the statehouse with a lower threshold for approval.

According to the Cincinnati Enquirer , this hybrid of state officials and a commission to determine redistricting would be a national first.

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