Here's a visualization of this; mostly bluer cities and mostly redder non-city:
But DC voted 93% Democrat in 2008. 93! That's not a majority. That's a consensus.
Democrats are pro-government, so DC votes for Democrats.
- 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
Here are the next-most-Democratic cities I came across in some spot-checking, with NYC boroughs broken out b/c they're separate counties: 89% Bronx (NYC), 86% Manhattan (NYC), 84% San Francisco, 80% Brooklyn (NYC), 79% Boston, 79% Alameda County (East Bay), 77% Portland.
Silicon Valley is closer to the 70-ish you're thinking of, but it includes a number of quite suburban areas. Obama won 74% in San Mateo County, and 70% in San Jose County. LA County is about the same (70%), as is Fulton County (Atlanta).
Santa Clara County? :-)
> LA County
Sorry, I guess we're a bit overly fussy out here. That one would be Los Angeles County. (Not that you couldn't call it LA County, just doesn't sound quite right. It's not uncommon to abbreviate the city to LA, but not so much the county.)
Do you have a source for that?