News Retired astronaut Mark Kelly to run as Democrat for John McCain’s Senate seat in 2020 February 12, 2019 William Cummings and Yvonne Wingett Sanchez, USA TODAY Comments Off on Retired astronaut Mark Kelly to run as Democrat for John McCain’s Senate seat in 2020 The election to finish McCain's last term will be held in 2020. The seat is currently held by Republican Sen. Martha McSally. McSally.