Last week, Rep. Ted Yoho (R-Fla.) announced he was retiring in 2020, making him the 19th Republican member of the U.S. House to do so. To date, four Senators (three Republicans and one Democrat) and 32 Representatives (23 Republicans and nine Democrats) are not running for re-election. In 2018, 55 total members of Congress—18 Democrats and 37 Republicans—did not seek re-election.

As of December 16, 2019, 313 candidates are filed with the Federal Elections Commission (FEC) to run for U.S. Senate in 2020. Of those, 268—143 Democrats and 125 Republicans—are from one of the two major political parties. In 2018, 527 candidates filed with the FEC to run for U.S. Senate, including 137 Democrats and 240 Republicans.

1,976 candidates are filed with the FEC to run for U.S. House in 2020. Of those, 1,847—912 Democrats and 935 Republicans—are from one of the two major political parties. In 2018, 3,244 candidates filed with the FEC, including 1,566 Democrats and 1,155 Republicans.

On November 3, 2020, 35 Senate seats and all 435 House seats are up for election. Of those Senate seats, 33 are regularly-scheduled elections, while the other two are special elections in Arizona and Georgia. Twelve are Democratic-held seats and 23 are Republican-held seats. In the House, where all the seats are up for election, Democrats currently hold a 233-seat majority.

Additional Reading:
United States Senate Elections, 2020
United States House of Representatives Elections, 2020
List of U.S. Congress incumbents who are not running for re-election in 2020