A little Historical perspective.
Why the President's Party Loses Seats in Midterm ElectionsThe President's Party Almost Always Loses Seats in Congress
By Tom Murse
Updated February 04, 2020Midterm elections are not friendly to the president's political party. Modern midterm elections have resulted in an average loss of 30 seats in the House of Representatives and Senate by the political party whose president occupies the White House.
Midterms, held in even years in the second year of a president's four-year term, are typically thought of as a barometer of the majority party's popularity among the electorate. And with few exceptions, they're pretty ugly.
Competing TheoriesThere are competing theories for why the president's party suffers in midterm elections. One is the belief that a president who is elected in a landslide, or because of a "coattails effect," will suffer deep losses in the midterms.
The "coattail effect" is a reference to the effect a very popular candidate president has on voters and candidates for office who are also on the ballot in presidential election years. Candidates of a popular presidential candidate's party are swept into office on their coattails.
But what happens two years later in the midterm elections? Apathy.
The University of Houston's Robert S. Erikson, writing in the Journal of Politics, explains it this way:
"The stronger the presidential victory margin or the more seats won in the presidential year and therefore 'at risk,' the greater will be the subsequent midterm seat loss."
Another reason: the so-called "presidential penalty," or the tendency of more voters to go the polls only when they are angry. If more angry voters vote than do satisfied voters, the president's party loses.
In the United States, voters typically express dissatisfaction with the president's party and remove some of his senators and members of the House of Representatives. Midterm elections provide a check on the president's power and give power to the electorate.
Worst Midterm Election LossesDuring the midterm election, one-third of the Senate and all 435 seats in the House of Representatives are at stake.
In the 21 midterm elections held since 1934, only twice has the president's party gained seats in both the Senate and the House: Franklin Delano Roosevelt's first midterm election and George W. Bush's first midterm election.
On four other occasions, the president's party gained Senate seats and once it was a draw. On one occasion, the president's party gained House seats. The worst midterm losses tend to occur in a president's first term.
Modern midterm election results include:<..snip..>
https://www.thoughtco.com/historical-midterm-election-results-4087704