That analysis looked only at U.S. House races, while the AP analysis also includes state legislative elections.
The formula compares the statewide average share of the vote that a party receives with the statewide percentage of seats the party won, taking into account that in politics, each percentage point share of statewide votes generally accounts for a 2 percentage point increase in seat share. But Republicans have a 7-4 majority in the state's congressional delegation and now control the state House 66-34.More news: Coyotes get D Niklas Hjalmarsson in trade with Blackhawks
The AP also calculated efficiency gap scores for U.S. House elections, translating those into estimates of extra seats won because of partisan advantages. That helped provide the GOP with a comfortable majority that stood at 241-194 over Democrats after the 2016 elections - a 10 percentage point margin in seats, even though Republican candidates received just 1 percentage point more total votes nationwide.
"The outcome was already cooked in, if you will, because of the way the districts were drawn", John McGlennon, a professor of government and public policy at the College of William and Mary and a Democratic politician, told the Associated Press. "The result in this decade's maps has been a persistent and consequential seat advantage in favor of Republicans that will likely endure for the remainder of the decade".
Even with the new lines from past year, Virginia's congressional district favors the GOP, the AP's analysis shows.More news: Four more Grenfell Tower victims identified
Districts underwent dramatic changes that broke decades of precedent: The map shifted whole counties and some of the state's larger cities into new congressional districts, and pitted two Democratic congressmen against each other to remain in Congress. Mapmakers apparently analyzed voting patterns of individual wards. That results in a 47 percent efficiency gap heavily favoring Democrats, but both races were close, and if fewer than 5,000 votes had switched in either district, the efficiency gap would be almost even. A similar analysis in 2014 showed Democrats had a slight advantage in the same districts. South Carolina's lone Democrat in Congress represents a district gerrymandered as majority minority. The U.S. Supreme Court has agreed to hear an appeal.
The "efficiency gap" formula creates a way to measure whether gerrymandering has helped a political party extend its power.
Still, experts say, Republicans generally benefit far more from gerrymandering than Democrats, since they hold control of the majority of state legislatures and governors' mansions.More news: Halle Open quarterfinals: Federer takes on defending champion
The national Republican State Leadership Committee, the force behind the party's surge in state legislative elections, attributes its victories to candidates who better represent their communities.