Ohio Republicans approved a new congressional map that could give the GOP control of 13 of the state’s 15 House seats, a net loss of two safe Democratic districts in a former swing state.

Passed by GOP supermajorities in both state legislative chambers this week, the updated boundaries are only good for the next four years since they didn’t have any Democratic support.

The map creates GOP-leaning or toss-up districts to replace the seats currently held by northeast Ohio’s Tim Ryan, who’s running for Senate, and Toledo’s Marcy Kaptur, the longest-serving woman...