[The Washington Post]

In the wake of the government shutdown and declining Republican popularity, Democrats are growing more optimistic about winning a majority in the House of Representatives in 2014.   Several recent polls show Democrats leading the “generic ballot” for Congress by eight or nine points.  Yet they still face an uphill battle; in 2012, Democrats won a majority of the congressional popular vote but a minority of seats, due to district maps biased against them through both partisan gerrymandering and asymmetric population distributions.   But just how steep is this hill?  How big of a national majority would Democrats need to win that 218th seat?

David Wasserman of the Cook Political Report estimates that it would take a 6.8 percent lead in the national vote for Democrats to win control.  And if ranked by vote share, the Republican candidate won the 218th seat by a similar amount (6.3 percent) in 2012.  But the 2014 electoral landscape might not mirror the 2012 congressional results, when Democrats concentrated so much more of their campaign efforts on retaining the Presidency and Senate.  If the House appears more competitive at a national level in 2014, it is likely that Democrats will field higher-quality candidates and devote more resources to these new swing seats.

Under two alternate methods, I estimate that Democrats could win the House with an even smaller lead in the generic ballot — a lead closer to 5 percent.  But there is still much uncertainty as to how much the bias from a previous cycle will carry over into future elections.

In 2012, Barack Obama was reelected with a 3.9 percent margin of the national popular vote, yet won only 209 of the nation’s 435 congressional districts. To have won a majority of districts, Obama would have needed to win nine more.  So one way to quantify any GOP bias in the congressional landscape is to ask: “How much more would Obama need to have won by in order to win nine more districts?”