COLUMBUS, Ohio (AP) - A political map-making process controlled by Ohio Republicans resulted in the party winning nearly two more U.S. House seats and five more Ohio House seats in the last election than would have been expected in neutral circumstances, an Associated Press analysis has found.
The AP used a mathematical formula to determine the effects of gerrymandering, in which the party in power alters voting districts to its advantage, in federal and state legislative races across the country. The analysis placed Ohio's "efficiency gap" near the top for both state and federal legislative races.
The analysis found Republicans won 56 percent of the votes in Ohio House races yet 66 percent of the seats. Republican candidates for Ohio's U.S. House seats won 58 percent of the votes but 75 percent of the state's 16 congressional seats.
Ohio has seen growing bipartisan concern about how its voting districts are drawn.
After a decade of false starts, Ohioans voted overwhelmingly in 2015 to approve new rules for drawing state legislative districts that aimed to reduce gerrymandering. The resulting new apportionment system emerged from an historic compromise between Republican and Democratic lawmakers that gives the minority party a powerful say on any new 10-year map designating Ohio's 99 House and 33 Senate districts.
Backers are working now to get a similar proposal overhauling Ohio's congressional map-making system on the statewide ballot. The idea of replacing a process that gives the state Legislature power to approve the maps drawn once every 10 years has support from Ohio Gov. John Kasich, a Republican.
Former Congressman Dennis Kucinich, who saw his Cleveland district eliminated after the 2010 Census and his home drawn into that of a fellow Democrat, said there's "no question" districts are unfair - though he holds both parties culpable.
"First of all, it wasn't that I was hurt personally," he said. "But the people in Cleveland were deprived of a congressional seat and remain deprived of a congressional seat, so that's always been, for me, a major injustice."
Betty Sutton, another northeast Ohio Democrat who lost her congressional seat in that redistricting, said her district was "a perfect example of partisan efforts to rig the system."
"When the special interests couldn't beat us at the ballot box, they stacked the district to get the result they wanted," she said.
For its analysis, the AP scrutinized all 435 U.S. House races in November using an "efficiency gap" statistical method designed to calculate partisan advantage. It found that the GOP may have won as many as 22 additional congressional seats than expected based on the average vote share in congressional districts across the country.
The AP's analysis was based on a formula developed by University of Chicago law professor Nick Stephanopoulos and Eric McGhee, a researcher at the nonpartisan Public Policy Institute of California. Their mathematical model was cited last fall as "corroborative evidence" by a federal appeals court panel that struck down Wisconsin's Assembly districts as an intentional partisan gerrymander in violation of Democratic voters' rights to representation. The U.S. Supreme Court has agreed to hear an appeal.
Stephanopoulos and McGhee computed efficiency gaps for four decades of congressional and state House races starting in 1972, concluding the pro-Republican maps enacted after the 2010 Census resulted in "the most extreme gerrymanders in modern history."
The efficiency gap formula compares the statewide average share of the vote a party receives in each district with the statewide percentage of seats it wins, taking into account a common political expectation: For each 1 percentage point gain in its statewide vote share, a party normally increases its seat share by 2 percentage points.
The AP used their method to calculate efficiency gaps for all states that held partisan House or state Assembly elections for all of their districts in 2016. It showed that Ohio provided the GOP with 1.6 extra U.S. House seats, the fifth highest nationally among pro-GOP states, and 5.23 extra seats in the Ohio House, the 12th highest nationally.