Midterm seat losses shrink as the initial House majority grows larger

Evidence

Although it is difficult to give each president an overall score on his relations with Congress, there are some objective measures that might reflect that relationship, including the number of rejections of court and cabinet appointments (taken from Kane, 1956) and the percentage of vetoes overridden (taken from U.S. Senate Library, 1976). A final aspect of a president’s political skill involves his party’s election success at the mid-term elections 2 years after the inauguration. Normally, the president’s party loses seats. In the House of Representatives, the percentage of seats lost varied inversely with the percentage size of the initial majority (r=−. for 24 midterm elections; percentages rather than raw changes in seats were necessary because of the changing size of the U.S. House of Representatives over time). — John T. Jost and Jim Sidanius, Political Psychology, 1343