Class 2 Senate seats in Minnesota and Mississippi each held special elections to fill vacancies. The Class 1 Senate elections were for terms lasting from January 2019 to January 2025 while the Class 2 special elections were for terms ending in January 2021. 24 of the seats up for election were held by Democrats, two of the seats up for election were held by independents caucusing with the Democrats and nine of the seats up for election were held by Republicans.[1] Three Republican incumbents did not seek election in 2018 while all Democratic and independent incumbents sought another term.