Republicans in Wisconsin tilted district maps in their favor in order to hamper Democrats and ultimately win state elections in 2012 and 2014, a federal court said on Monday in a case that could influence future rulings on gerrymandering.
The United States District Court for the Western District of Wisconsin decided 2-1 that Act 43, a redrawing of districts approved by the state's Republican-led legislature in 2012, violated the U.S. Constitution, court documents showed.
"We find that the discriminatory effect is not explained by the political geography of Wisconsin nor is it justified by a legitimate state interest," the court wrote in its ruling.
The case has no bearing on Donald Trump's victory in Wisconsin in the presidential election on Nov. 8, in which he defeated Democrat Hillary Clinton.
Wisconsin Attorney General Brad Schimel said in a statement that he planned to appeal, which would send the case to the U.S. Supreme Court.
A ruling there on gerrymandering - the practice of manipulating electoral boundaries for political advantage - could have wide implications across the country as similar cases in Maryland and North Carolina work their way through lower courts.
"This is a big victory for those who want to see courts rein in partisan gerrymandering. But it is anybody's guess what happens to this when it gets to the Supreme Court," wrote Richard Hasen, an elections law expert at the University of California, Irvine, on his blog.
Since 2010, Republicans have more than doubled their control of state legislatures. They now control both legislative chambers in a record 32 states, The New York Times reported.
"Republicans win elections because we have better candidates and a better message that continues to resonate with the voters," said Republican Assembly Speaker Robin Vos in a statement.
Twelve Wisconsin voters argued in their lawsuit that Republicans redrew maps in 2011 to divide Democratic voters so they fall short of a majority in districts and to concentrate Democratic voters into districts so they win by overwhelming margins and dilute votes of Democrats statewide, according to the ruling.
Despite receiving 51 percent of the votes statewide in 2012, Democrats won only 39 of 99 Assembly seats. In 2014, Republicans won roughly the same percentage of votes statewide, but won 63 seats, a 24-seat disparity, judges wrote.
The Wisconsin case hinged on a new way to measure the discriminatory effect of gerrymandering. The "efficiency gap" measure found the redistricting in Wisconsin caused Democrats to waste more votes than Republicans.
The measure gives judges "a clear threshold for deciding what is acceptable", Barry Burden, the director of the Elections Research Center at the University of Wisconsin-Madison, told the New York Times.