The belief that larger majorities for an incumbent president

The belief that larger majorities for an incumbent president in a presidential election help the incumbent’s party increase its representation in the House and Senate is called the coattail effect. The file P14_54.xlsx gives the percent by which each president since 1948 won the election and the number of seats in the House and Senate gained (or lost) during each election. Are these data consistent with the idea of presidential coattails? (Source: Wall Street Journal, September 10, 1996)