Democrats had large majorities when Jimmy Carter became president in 1977 (61-38 in the Senate, 292-143 in the House) and when Bill Clinton took office in 1993 (56-44, 258-176). So why are their prospects for legislative success so much better now?
The most significant change is in the ideological makeup of the Democratic majorities. In the Carter and Clinton eras, there were dozens of moderate and conservative Democrats in Congress, a disproportionate number of them committee chairs. Now the Democratic majorities in both houses are composed almost uniformly of liberals. Those few who aren’t, including the tiny but heralded gang of moderates elected to the House in 2006, usually knuckle under on liberal issues. House Speaker Nancy Pelosi bosses them around like hired help.