Midterm losses. The president's party almost always loses seats in midterm elections. The graphic below (from Vox) illustrates the trend. It shows that only 2 of the 18 midterm elections (for the House) between 1946 and 2014 bucked the trend. (It also shows that the average midterm loss in the House for that period was 25 seats.)
"Midterm losses" for the president's party are the norm, and not just in the postwar era. In 150 years from 1852 to 2002, only two midterm elections bucked the trend.
Why do midterm losses occur? Two basic reasons. (1) Voter turnout tends to favor the president’s opponents in midterm elections. Defenders of the president are less motivated to get to the polls than the president's opponents. (2) A president and his party tends to be less popular at midterm than when he was elected. In presidential elections, the more popular candidate or party tends to win, and the partisan “tide” or the candidate’s “coattails” also help the party in congressional elections. Two years later, the popularity of the president and/or his party tends to be lower, and the tide may go the other way.
"Midterm losses" for the president's party are the norm, and not just in the postwar era. In 150 years from 1852 to 2002, only two midterm elections bucked the trend.
Why do midterm losses occur? Two basic reasons. (1) Voter turnout tends to favor the president’s opponents in midterm elections. Defenders of the president are less motivated to get to the polls than the president's opponents. (2) A president and his party tends to be less popular at midterm than when he was elected. In presidential elections, the more popular candidate or party tends to win, and the partisan “tide” or the candidate’s “coattails” also help the party in congressional elections. Two years later, the popularity of the president and/or his party tends to be lower, and the tide may go the other way.