States with largest difference between large and small counties:
Heavily minority large counties and lily white hillbilly small counties.
That's Maryland in a nutshell, especially in Western Maryland (Washington, Allegany, and Garrett counties, with heavy emphasis on the last two, as Hagerstown, which is in Washington County, isn't seen to be as "Western Maryland" as it used to be--although it still made me laugh when the crew on Morning Joe saw Ben Cardin being heckled there at a town hall and were surprised because Maryland is a Democratic state--Hagerstown may not be Garrett County, but it isn't Prince George's County, either), the most Republican area in the state, where I go to school.
Southern Maryland meanwhile (Charles, Calvert, and St. Mary's counties), where I grew up, although definitely not the liberal and/or Democratic bastion that the DC suburbs and Baltimore and its surrounding suburbs are (excluding some areas like Anne Arundel County outside of Annapolis), is not as Republican as one might think. Charles County has gone Democratic since 2000 (although it's also more urban than it was before 2000, and is the closest to DC of the Southern Maryland counties--go figure-- but there are still rural areas in that county, though, just not as many as there used to be).
In St. Mary's County, there is actually a fairly significant African-American population, but it is offset by the large military population due to the presence of the Patuxent River Naval Base. Western Maryland, on the other hand, has neither (again, in terms of ethnicity, go figure--it's the part of the state that borders West Virginia and Southwestern Pennsylvania).
Southern Maryland is the fastest growing area of the state, though, so it'll be interesting to watch elections there in the next few years.