11/01/2006 - In recent decades, there have been three basic ways that turnout has worked to produce the sort of "big wave" midterm election results that the Democrats are hoping for next week, according to analysis by the Pew Research Center.
First is the "one-party surge," where one of the parties significantly increases its vote from the previous midterm while the other party's vote remains essentially unchanged. That is what happened in 1994, when Republicans won control of both houses of Congress. The nationwide GOP congressional vote spiked by more than 9 million votes from 1990, the biggest increase in one party's vote from one midterm to another since World War II. Meanwhile, the Democratic total declined by 400,000 votes.
Another way to produce a big change in Congress is a "one-party collapse," where a huge number of voters from one of the parties simply sit out the election. That is what happened in 1974, when the dispiriting backdrop of the Watergate scandal led to a nearly 3-million vote falloff in the Republican House vote from 1970. The Democratic vote grew by barely 1 million. But the GOP drop off was so severe that it cost the Republicans nearly 50 House seats.
A third way to effect considerable change in Congress is what might be called "unequal gains," where both parties add votes from the previous midterm but one party gains far more than the other. That happened in 1982, President Reagan's first midterm, when the Republican congressional vote grew by more than 3 million from 1978, but the Democratic tally swelled by more than 6 million. The result: a gain of roughly two dozen House seats for the Democrats.
Read the full report Voter Turnout and Congressional Change on the Pew Research Center Web site.