A great analysis of the problem by Peter Shane,
Within moments of President Obama’s apparent victory in both popular and electoral votes, Speaker Boehner was claiming that Republicans enjoy their own mandate from the 2012 elections – Republicans kept control of the House. I’m searching in vain for a polite word for this argument.
With unemployment still near 8 per cent and a majority of voters thinking the country is on the wrong track, the Democrats nonetheless not only retained the White House, but increased their majority in the Senate and racked up a string of victories, coast-to-coast, for unmistakably progressive causes and candidates. They won these victories because, in a head to head contest with opposing views, the Democratic or, more generally, the progressive, view proved more appealing.
The reason why the Republicans still have the House is simple: gerrymandering. According to NYU’s Brennan Center for Justice, Republicans used their complete control of 17 state governments after the 2010 elections to pack Democrats into fewer “safe” Democratic districts and create 11 additional “likely” seats for Republicans – that is, seats where the GOP could be expected to routinely receive 55-60% of the vote in a two-party contest.
–Peter Shane, The Two-Mandate Myth: An Ohio View.