When you look at partisan voting behavior in Maryland, you see that the state is neatly divided by the portion of the megolopolis that runs the state. Pee-Gee, Montgomery, Harurd, An'Rundul, Bahlmur, and Bahlmur Ciddy. But when you look at the other 17 counties you see blue.
Here is a nice shot from USGS's "The National Atlas"
Funny - what is the standard for blue and red maps? I found maps that portrayed the parties in both colors. I believe that the Dems should be shown as red (because they are!)