|There were three districts that John McCain won that Barack Obama won 4 years later:
Two of these are in Miami-Dade county, Florida, an area Obama really improved in, while the other is primarily in Staten Island, where the voting was disrupted by Sandy.
The list of districts Barack Obama won in 2008 and Romney won in 2012 is much longer.
One of the reasons it's longer is because Romney did better than McCain. Obama won CA-25 in 2008 48.7%-48.1%, but lost it in 2012 47.8%-49.7%. The district, however, still had a PVI of R+3.
The list contains 4 districts in Illinois, 7 in Michigan, 5 in Pennsylvania, and 4 in Wisconsin. While Romney did noticeably improve on McCain in these states, the best of them, Illinois, was actually the state Romney improved 9th best. These states just consist of a bunch of swingy R+1-3 districts that Obama won narrowly in 2008 but lost in 2012.
Democrats have congressmen in 9 districts Mitt Romney won.
Republicans have congressmen in 17 districts Barack Obama won.
Before we conclude that this is a big advantage for Democrats, we have to remember that since Barack Obama won the election, he won several Republican leaning districts. If we adjust the lists and add in districts held by Democrats with a Republican PVI, that list goes from 9 districts to 15.
On the other side, if we exclude districts that Obama won, but have a Republican PVI from the Republican list, we go from 17 to 10.