Another reason Democrats will have difficulty retaking the US Senate this fall: Republicans' historical advantage in holding open seats

This fall, the Democrats face a challenging US Senate map, defending 25 seats to the GOP's nine. For some on the left, one ray of hope has been the retirement of four Republican Senators, leading to open seat contests. In new research, Hanna K. Brant, L. Marvin Overby, and Theodore J. Masthay suggest that this optimism may be misplaced. Studying nearly a century of Senate elections, and accounting for a number of other factors, they find that Republicans have a roughly ten percent advantage over Democrats in winning open Senate seat races.