A similar analysis in 2014 showed Democrats had a slight advantage in the same districts. That's a spike upward from about 50 percent uncontested races in the previous two elections, and around 40 percent during the first decade of the 2000s. Florida was found to be one of the states with the largest Republican tilts in the state House.
Although most of Missouri's unopposed candidates were incumbents, some newcomers seeking open seats also cruised to victory without major-party opponents.
Call said he hoped the Wisconsin case could prompt changes in how Colorado goes about drawing its legislative districts - though those changes would require longshot amendments to the state Constitution and to statute.
Senate Democratic Leader Chuck Schumer says Senate passage of the Republican bill to replace former President Barack Obama's health law is too close to call.
"The Democrats don't know how to run campaigns; they're disgusting at it", he said.
"There's one answer for that, one word: gerrymander", said Terry Madonna, director of the Center for Politics and Public Affairs at Franklin & Marshall College in Lancaster, Pennsylvania.More news: FIFA Confederations Cup: Portugal, Mexico through to semi-final
Missouri's 163 House districts were drawn in 2011 by a six-member panel of state appeals court judges after a bipartisan citizens' commission failed to agree on a plan. Democrats lost four seats to Republicans. Their final map, agreed to unanimously, didn't mirror any particular one of those recommendations.
Republicans on average won 64 percent of the votes in each district, but they won 83 percent of all state House seats. "And I think that's what we did", Republican Party of Kentucky spokesman Tres Watson said.
Missouri's redistricting office analyzed the new House districts in 2011 by applying a decade of past election results.
Republican lawmakers have steadfastly defended the state districts lines as legal and fair, and noted that many GOP candidates have won in districts that Democratic in presidential elections. That analysis looked only at U.S. House races, while the AP analysis also includes state legislative elections.
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. The formula seeks to identify "wasted votes", defined as any vote for a losing candidate or any vote for a winning candidate beyond the 50 percent threshold required to win. Idaho has a 13 percent efficiency gap heavily favoring Republican congressional candidates. Republicans may have won an extra congressional seat over what would have been expected based on the average vote share around the state that shows a large so-called "efficiency gap".
Republican state Sens. Dan Soucek, left, and Brent Jackson, right, review historical maps during The Senate Redistricting Committee for the 2016 Extra Session in the Legislative Office Building at the N.C. General Assembly, Feb. 16, 2016, in Raleigh, N.C. An Associated Press analysis, using a new statistical method of calculating partisan advantage, finds traditional battlegrounds such as Michigan, North Carolina, Pennsylvania, Wisconsin, Florida and Virginia were among those with significant Republican advantages in their USA or state House races in 2016.