How gerrymandering cost Democrats the House in 2012: Part 1: An interactive look at alternative maps

http://www.dailykos.com/story/2015/05/13/1382504/-How-gerrymandering-cost-Democrats-the-House-in-2012-Part-1-An-interactive-look-at-alternative-maps
"In November 2012, the American electorate voted to give Democrats unified control of government. President Obama won re-election with a majority of the vote, Senate Democrats increased their seat count, and Democratic candidates for the House won the popular vote. However, because of the way in which districts are drawn, Republicans easily maintained control of the House."