in another thread on why we have a Democratic president and a Republican Congress, there was a New York Times article that Democrats win urban areas big whereas Republicans more narrowly win a larger number of rural and suburban (and exurban) areas. All House districts have the same population of about (?)750,000 persons.
http://mobile.nytimes.com/2014/09/0...istory.com/discussion/showthread.php?t=377137
It is a mixture of factors, one being of course gerrymandering, which both sides do (I live in MD, so I can attest to the Democrats not being above that kind of bullshit), but the Republicans are just better at it. But beyond that, it is also because the Republicans have basically abandoned many cities and have written them off as unwinnable. Their candidates in cities get almost no support from the national party in terms of money or any kind of logistical volunteering, and many are self funded local businesspeople. This leads to events occurring like Mitt Romney not winning a single vote in certain urban precincts in 2012.
Why has Detroit not elected a Republican in 40 years? Its not because the Democrats are doing a good job, its because the GOP does not make an effort to win elections there.
The GOP has regionally tailored their politics in a way that the Democrats have trouble doing despite being at war with itself, and has legislative agendas at the state level through ALEC that allows it to mobilize the amount of support that it has to the max to get things done. Congress may be dysfunctional and inactive, but GOP State Legislatures are not. And to be honest, as a Republican, I kind of like this, as states really should be doing almost everything in my view.