One thing that one has to keep in mind when talking about the Democratic congressional majority, especially in the house before the Democratic Study Group led by the late Phil Burton of San Francisco was that the bulk of Democrats from the south were very conservative, not just on social issues, but economic issues as well. After 1974, comittie assignmnets were no longer based on senority, but by a vote in the Democratic house membership, so party discipline amoung southren Democrats increased.
Even then, up though the late 80s, there were about 30 or so conservative Democratic house members from the south who voted the conservative position on a majority of issues. Of course there were also a contingent of liberal Republicans from the Northeast was well, but they were less numerous.
And the group of 30 were pretty much wiped out in the 1994 Gingrich Republican revolution when the Republicans picked up 54 seats.
