More info:

- Many in the DC metro area are also employed by the military or employed by proxy (i.e. working for a contractor like Boing/Lockheed/Caci/etc.).

- The military is a part of the government.

- The republican party is firmly behind the military.

Unsurprisingly the outlying suburbs of the DC metro area are lean republican[1].

Looks like everyone is voting for their own interests here.

[1] http://www.princeton.edu/~rvdb/JAVA/elections/Multiyear3.gif

I don't think that's true of the past decade or so. While DC's outlying suburbs in Virginia and Maryland are more Republican than the urban core, they most certainly vote more Democratic than the average suburban county elsewhere in the U.S.

It's possible that is a factor, but DC is >50% black, so it wouldn't be surprising to see a huge majority for Obama in 2008.

It's about 50% (50.7) http://quickfacts.census.gov/qfd/states/11000.html

It's been as high as 71.1% Black (in 1970). The percentage has been decreasing as Blacks have moved to the suburbs and Hispanics have moved into the city.

Well, I would argue a large number of young white professionals have moved in to and are gentrifying many parts of DC.

I agree that this is the bigger trend changing the demography of DC. Neighborhoods like Columbia Heights, Petworth, etc.

The metro DC region is one of the most educated areas of the country. This is the reason why the area leans more blue than red.

Cities are necessarily liberal entities, and people who live in cities tend to vote for more liberal parties.