News from Wisconsin:

A group of Democrats sued state election officials Wednesday over election maps Republicans drew in 2011 that helped give them a firm grip on the Legislature.

The lawsuit comes two years after a panel of three federal judges in separate litigation redrew two Assembly districts and blasted GOP lawmakers for drawing the maps in secret. That panel found the two districts on Milwaukee’s south side violated the voting rights of Latinos, but it left in place all the other legislative maps, allowing Republicans to keep their advantage in elections.

The new lawsuit seeks to change that by arguing the maps are so partisan as to be unconstitutional….

The U.S. Supreme Court has ruled overly partisan maps can be unconstitutional, but the justices have never agreed on what standard to use to determine that. The latest lawsuit proposes a way of doing that.

Partisan gerrymandering is achieved by “cracking” and “packing” districts. Cracking districts involves breaking up voters of one party across multiple districts so they don’t have a majority of votes in the districts. Packing districts amounts to stuffing large number of like-minded voters into a small number of districts.

In both cases, those districts produce large numbers of “wasted” votes — that is, excess votes that aren’t needed to elect a candidate. Those bringing the lawsuit contend partisan gerrymandering can be measured by using those wasted votes to calculate a redistricting plan’s “efficiency gap.”

The gap is the difference between the two parties’ wasted votes divided by the total number of votes cast. The gap determines the percentage of seats a party receives that it would not have received under a plan in which both sides receive roughly equal numbers of wasted votes.

Using that measure, the Assembly maps gave Republicans an efficiency gap of 13% in 2012 and 10% in 2014. That makes the maps one of the most partisan in American history, according to the lawsuit.