Throughout the 1990s MD's Congressional district was split between four Democrats and four Republicans. The old map appears here:
As you can see the old 2nd district, which elected Ehrlich to Congress, was logical. It was basically Baltimore and Harford Counties. That suburban Baltimore seat leaned Republican. Even though it had more Democrats than Republicans.
The old 8th, which was part of Montgomery County, elected liberal Republican Connie Morella (R). She was a "misfit"--she was a Republican representing one of the most Democratic seats in the country. She was well-liked and key Democrats in the county never ran against her until Van Hollen unseated her last year.
The 6th, which Barlett represents now, used to elect Beverly Byron (D) to Congress. She held the seat from the late 1970s through 1992, when a Democrat upset her in the primary. Tom Hattery was his name, I believe. And he lost to Bartlett that cycle.
The 1st, the other Republican seat, was the Eastern Shore. The shore is heavily Republican and has been since the 1960s. That part of Maryland, along with the Panhandle, turned Republican when the National Democratic Party swung to the left. Wayne Gilchrest has represented this seat since 1990, when he defeated Roy Dyson (D).
The new map for this decade appears here. What you notice is that all of the districts are misshapen and look very bizzare. The Democrats basically threw Morella and Ehrlich into the 1st and the 6th districts.
The new 2nd District, which now picked up crucial precincts in Baltimore City, gave up territorty in N. Baltimore County and in Harford County. Those precincts went to the 1st and to the 6th. Instead of overlapping with Baltimore and Harford County, the new 2nd extends like a claw into Baltimore City. It follows I-95 into Baltimore and takes in the immediate suburbs of the City. The old 2nd gave Bush II 55% of the vote. The new 2nd gave Gore a majority. The new 2nd was much more hostile to Ehrlich, so he vacated it to run for Governor.
The 2nd had not elected a Democrat since the 1980s. Helen Bentley and Bob Ehrlich were able to hold the old 2nd for the Republicans. Although both the old and the new 2nd have overwhelming Democratic regristration, the Democrats in the old 2nd were more than willing to vote Republican. Indeed the old 2nd never voted for Clinton or Gore.
The 1st and the 6th districts took away crucial precincts needed for the 2nd and the 8th districts from the Republicans. Northern Montgomery County went to Roscoe Batlett. Norther Harford and Baltimore County went to Bartlett and Gilchrist.
The 6th district is Republican because it takes in the "white flight counties" of MD. It takes in Frederick and Carroll County, which are growing really fast. Those counties include a lot of "white flight" that is fleeing the closer suburbs of Baltimore and Washington. Ehrlich's crushing 3-1 margins in Carroll, Harford, and Frederick counties. Redistricting gave all of these areas to Barlett so that Morella would not have Damascus, in Northern Montgomery County, to give her crucial votes. Damascus is one of the few Republican leaning areas in Montgomery County.
The 8th district elected Van Hollen (D) in 2002. The new 8th district gave up the Northern part of the County to the 4th and to the 6th district. The seat gained crucial votes in PG County. It picked up the towns of Takoma Park, Riverdale, Bladensburg, Colmar Manor, and Mt. Rainer. These precincts enabled Van Hollen to defeat Morella.
Morella was an anomaly, as I had said. But she was really popular. After she first won her seat in 1986 she was routinely able to win comfortably. Key Democrats in the County respected her and worked with her. Through the 1990s she was able to win with 70% of the vote or more even though Democrats were winning other offices in the area.
Then, in 1998, Ralph Neas, the director of People for the American way, held her to 60%. While it was still a comfortable win for Morella it was significant lower than her previous showings. Then, in 2000, Terry Lieberman held her to 45% when he ran against her and very well might have won had he not found himself in a scandal with neighboring Democrat Jim Moran, who represents the Arlington area in Congress.
Thus the new MD map maximizes Democratic opportunities in the seats that encompass the Baltimore-Washington area. It basically pushes all the state's Republicans into two seats. It concedes the exurbs of Washington and Baltimore, along with the Eastern Shore and the Panhandle, to the Republicans. They designed the map so that it would elect 6 Democrats and 2 Republicans, which is exactly what happened in 2002.