Among the two dozen most populated states that determine the vast majority of Congress, there were nearly three times as many with Republican-tilted U.S. House districts. Traditional battlegrounds such as Michigan, North Carolina, Pennsylvania, Wisconsin, Florida and Virginia were among those with significant Republican advantages in their U.S. or state House races. All had districts drawn by Republicans after the last Census in 2010.

New quantitative approaches—measures of how biased a map is, and algorithms that can create millions of alternative maps—could help set a concrete standard for how much gerrymandering is too much ... some of these new approaches helped convince a United States district court to invalidate the Wisconsin state assembly district map—the first time in more than 30 years that any federal court has struck down a map for being unconstitutionally partisan.

In California, voters passed ballot measures...that took power to draw political maps away from the Legislature and handed it to an independent citizens commission made up of five Democrats, five Republicans and four people not affiliated with a major party. Politicians, lobbyists and campaign donors are not eligible to serve on the commission. California is the only state that’s removed politicians from the map-drawing process...15 other states have taken the authority away from the legislature

the consequence of gerrymandering in the South has resulted in a significant underrepresentation of Democrats among the region's congressional delegates. In 2012, 41 percent of Southerners voted for a Democrat, but Democrats made up only 29 percent of U.S. representatives from the South. That meant Southern Democratic voters were four times more likely to be underrepresented in Congress than the national average.

The US also ranks 52nd out of all 153 countries worldwide in the cross-national electoral integrity survey. The comparison is even worse for the issue of district boundaries, where the U.S. score is the second lowest in the world ... the worst in electoral integrity among similar Western democracies.

there are bedrock principles in a constitutional democracy: that majority wins and constitutional rules, so far as they are clear, are respected. Gerrymandering and voter suppression throw majority rule into question—and changing the rules after an election is not in the spirit of constitutional consistency. It is the behavior of people who feel that they owe the other side nothing ... North Carolina has become a microcosm of the country’s hyper-partisan politics and growing mutual mistrust.

Numerous times since the civil rights era, courts have struck down how partisan state legislatures set up legislative districts on the grounds that those decisions diminished the political power of racial minorities. But courts have been far less likely to intervene in cases where states organized voting districts to boost one party, preferring to not get involved in explicitly political matters ... more significant change could come following a ruling by the Supreme Court

Weirdly-shaped congressional districts aren’t necessarily gerrymandered. Illinois’s 4th Congressional District looks like a jagged horseshoe. Mathematically, it looks like the worst example of gerrymandering in the US. But it’s actually a logical, urban Latino district ... if you didn’t carve this winding, circular district out of its urban surroundings in Chicago, the people who lived there would find it harder to make their voices heard in politics.