Explaining the Republican "Lock" on the U.S. House by Alan I. Abramowitz and Steven Webster
The results of recent national elections in the United States have followed a clear pattern: Democrats have dominated presidential elections while Republicans have dominated congressional and especially House elections. Since 1992, Democratic candidates have won four of six presidential elections and the popular vote for president five times out of six. At the same time, Republicans have won a majority of seats in the House of Representatives in nine of 12 elections and a majority of seats in the Senate in six of 12 elections. As a result, Democrats have controlled both chambers of Congress for only six of the past 22 years.