In the last Congressional elections in 2012, Democrats won more total votes than Republicans nationwide, and in Ohio, Pennsylvania, Michigan, North Carolina and numerous other states.
Despite that fact, the GOP holds large majorities in those states' House delegations. In Pennsylvania, for example, though Democrats out-polled Republicans in congressional voting by a substantial margin, the GOP holds 13 of that state's 18 congressional seats. In Ohio, it's a similar story, with the GOP holding 12 of 16 seats, despite being out-voted statewide by the Democrats.
It's that way because following the 2010 Census, in states whose legislatures were controlled by ALEC-led Republicans, an absurd amount of gerrymandering took place. Democratic voters in those states were Balkanized into very few districts using ridiculous geographic contortions. It's outrageous, and it's a primary reason we have the current Congressional stalemate.
It also explains how the GOP can get trounced in presidential elections and lose the Senate, but somehow control the House of Representatives despite getting fewer Congressional votes. Salon has put together a fascinating interactive puzzler to demonstrate the absurdity of the gerrymandering.
Wondering how so many nutbags got into the House of Representatives? Wonder no more.