The AP has this insightful article (remember… all my graphics are typically linked):
….Democrats blame Republicans for drawing districts that favor GOP candidates. “We’ve never seen a level of gerrymandering as severe as in 2010,” said Matt Bennett, a former aide to President Bill Clinton.
But some experts say geography may be just as responsible as gerrymandering for the Republican advantage.
Living patterns in many states make it relatively easy to pack Democrats into fewer congressional districts because they are much more likely than Republicans to live in dense urban areas, said Norman Ornstein, an expert on Congress at the American Enterprise Institute. Republicans are more likely to live in suburban areas, which can be more politically diverse, or in geographically large rural areas.
“Democrats are at a disadvantage here,” Ornstein said. “It’s not as difficult for Republicans doing a redistricting to concentrate the Democrats in districts where they can win 80 or 85 percent of the vote.”
But aggressive gerrymandering isn’t always necessary for Republicans to gain an edge, said Thomas Mann, an expert on Congress at The Brookings Institution.
“A lot of the Republican advantage — by no means all of it — a lot of it is the result of living patterns,” Mann said.
Two political scientists, Jowei Chen at the University of Michigan and Jonathan Rodden at Stanford University, are popularizing the idea that geography is more important than gerrymandering. They did a study using computer simulations to see whether the political makeup of Congress would be any different if congressional maps were drawn without partisan bias.
“In the vast majority of states, our nonpartisan simulations produced Republican seat shares that were not much different from the actual numbers in the last election,” Chen and Rodden wrote in a New York Times article. “In short, the Democrats’ geography problem is bigger than their gerrymandering problem.”….
Real Clear Politics has this piece back in the middle of 2013… which plays into some persons thinking this 2014 election sweep: