Gerrymandering is one of those topics that can get the blood boiling in most voters. But to defeat the practice in Pennsylvania, a team of lawyers took a more dispassionate approach—laying out the numbers before the state's highest court to show that Pennsylvania's congressional voting districts were horribly skewed in favor of one party.

On Jan. 22, the Pennsylvania Supreme Court ruled 5-2 in League of Women Voters of Pennsylvania v. Commonwealth of Pennsylvania that the Congressional Redistricting Act of 2011 was unconstitutional—a victory for the Democratic voters who challenged the Republican-controlled legislature's current districting layout.

The impact goes beyond Pennsylvania. It could potentially tip the scales in 2018, as Democrats make a bid to retake the House of Representatives in Washington, D.C.

The team behind the historic decision was a coalition of attorneys from the Public Interest Law Center in Philadelphia and Arnold & Porter Kaye Scholer in Washington, D.C., who also worked together in 2012 to strike down Pennsylvania's voter ID law.

Mimi McKenzie, the legal director of the Public Interest Law Center, and David Gersch, who led the Arnold & Porter pro bono team in the litigation, said computer models, maps, dates and common sense are what won the day in their representation of the League of Women Voters.

And in a stroke of poetic justice, the same tools state lawmakers used to draw maps in their favor were used against them in the court room.

“Advancements in technology, in mapping software, being able to load data into mapping software—all of that allows parties in control to carefully engineer maps to their advantage,” McKenzie said, adding that “the very technology that allows legislators to gerrymander, also helps us detect partisan gerrymandering.”

The team used data from three separate election cycles to provide evidence of gerrymandering, showing that Republicans win the same 13 districts to the Democrats' five every time.

“The Republicans have this 13-5 built-in advantage in the way that the map is drawn, and that has held even though there are natural swings in the vote from election to election,” McKenzie said.

According to Gersch and McKenzie, one expert, University of Michigan political science professor Jowei Chen, used traditional redistricting criteria to randomly create a thousand maps, which compared to the current congressional map, shows the current map is an extreme outlier in terms of partisanship.

Another was Wesley Pegden of the Carnegie Mellon University's mathematics department. He employed the Markov chain analysis to the study of Pennsylvania's districts. He input the current congressional map into a computer program and made slight changes to the edges of the districts. The result is that when a precinct is slightly altered, the 13-5 advantage disappears, Gersch said.

“All these different metrics taken together is what allowed us to prove this map intentionally discriminates against those who vote Democratic,” McKenzie said.

And according to Gersch, the state Supreme Court seemed to recognize that from the beginning. Oral argument was simply a formality.

“I think they had largely decided the case in our favor on the briefs. The real question was on the remedy, the things that could be done,” Gersch said.

The remedy came swiftly. Days after argument, the Pennsylvania Supreme Court issued an order to the legislature for the immediate drafting of a new congressional map. If lawmakers and Gov. Tom Wolf failed to agree on a plan before mid-February, the court would come up with something itself.

Republican lawmakers were not enthused by the order and accused the majority-Democrat court of political gamesmanship.

The ruling “is a partisan action showing a distinct lack of respect for the constitution and the legislative process. The Pennsylvania Supreme Court has overstepped its legal authority and set up an impossible deadline that will only introduce chaos in the upcoming congressional election,” said a joint statement from Senate President Pro Tempore Joe Scarnati and Senate Majority Leader Jake Corman.

On Thursday, Republican lawmakers asked the U.S. Supreme Court to issue an emergency stay.

But Gersch and McKenzie said Scarnati was playing games of his own during the litigation.

“From the outset, we were met with nothing but delay from the legislative respondents,” McKenzie said of attempts to retrieve discovery from the defendants, as well as the legislators' motions for stays and bid to remove the litigation to federal court.

“I've never seen anything like this,” Gersch said.

In the end, though, Gersch said the collaboration and teamwork between to two firms helped carry the day. In addition to McKenzie and Gersch, the team consisted of Ben Geffen and Michael Churchill from the Public Interest Law Center and John Freedman, Dan Jacobson, Stanton Jones and Elisabeth Theodore from Arnold & Porter.

“We had a great team,” Gersch said. “This case was stayed until Nov. 9, we had to go to trial Nov. 11 and we were at the Supreme Court last week. We had to mount a very sophisticated case in a very short time.”