From Ian Millhiser at ThinkProgress:
As of this writing, every single state except Hawai’i has finalized its vote totals for the 2012 House elections, andDemocrats currently lead Republicans by 1,362,351 votesin the overall popular vote total. Democratic House candidates earned 49.15 percent of the popular vote, while Republicans earned only 48.03 percent — meaning that the American people preferred a unified Democratic Congress over the divided Congress it actually got by more than a full percentage point. Nevertheless, thanks largely to partisan gerrymandering, Republicans have a solid House majority in the incoming 113th Congress.
A deeper dive into the vote totals reveals just how firmly gerrymandering entrenched Republican control of the House. If all House members are ranked in order from the Republican members who won by the widest margin down to the Democratic members who won by the widest margins, the 218th member on this list is Congressman-elect Robert Pittenger (R-NC). Thus, Pittenger was the “turning point” member of the incoming House. If every Republican who performed as well or worse than Pittenger had lost their race, Democrats would hold a one vote majority in the incoming House.
Hence, the Democrats need a +7% swing to regain the House given the current structure of House districts.