Former astronaut Mark Kelly, who ousted incumbent Republican Martha McSally in last month’s election, was sworn in Wednesday as a U.S. senator from Arizona.

Kelly, a Democrat, will serve the remaining two years in the seat once held by longtime Senator John McCain, a prisoner of war in the 1960s in Vietnam and the Republican presidential candidate in 2008. McCain died in 2018 after having served two years of a six-year term. McSally was appointed to replace him in 2018 but lost to Kelly in a special election.

Kelly will be up for a full six-year term in the 2022 election. He was sworn in by Vice President Mike Pence.

He is the husband of former U.S. Representative Gabrielle Giffords, who survived an assassination attempt by a gunman in 2011. Since then, she and Kelly have become vocal gun control advocates. Giffords watched her husband’s swearing-in from the Senate gallery.

Kelly’s victory gave Democrats control of the Southwestern state’s two Senate seats for the first time in more than six decades as the traditionally Republican state, with a growing Hispanic population, has turned into a political battleground.

President-elect Joe Biden defeated President Donald Trump in Arizona, the first Democratic presidential contender to win the state since 1996.