Former astronaut and U.S. Navy captain Mark Kelly was sworn in to the U.S. Senate Wednesday by Vice President Mike Pence, more than a month before the new Congress begins.

Sen. Kelly won a special election against now former Senator Martha McSally, who was appointed to the seat after Senator John McCain’s death in 2018. His election flips the seat from Republian to Democrat and reduces the Senate’s Republican majority to 52-48.

With Arizona Sen. Kyrsten Sinema (D-az) at his side, Sen. Kelly took the oath of office, followed by an elbow bump from Vice President Pence and applause from the other senators on the floor. He’ll serve out the last two years of Sen. McCain’s term, and he’s eligible for reelection in 2022.

The day before his swearing-in, he visited the grave of the late Arizona Sen. John McCain (R) with his wife, former Rep. Gabrielle Giffords.

“Senator McCain has been a hero of mine since I was a young pilot,” Kelly wrote on Twitter. “He left a legacy of service to Arizona and country that can’t be matched, but that we should all strive towards.”

Kelly's wife, former Congresswoman Giffords, was nearly killed in a shooting in Tucson, AZ, in 2011, and he's said he'll prioritize the issue of gun safety along with others such as health care, veterans and the economy.

Sen. Kelly won the seat by more than 78,000 votes, and his election marks the first time in decades that Arizona will have two Democratic senators in Washington. Before Sen. Sinema’s election in 2018, the state hadn’t chosen a Democrat for a seat since 1988.

President-elect Joe Biden congratulated Kelly on Twitter, adding "I look forward to working together to build this country back better."

Former Sen. McSally spoke from the Senate floor for the last time before Thanksgiving, and during a Tuesday hearing, she was recognized for her work in Washington by multiple colleagues on the Senate’s banking committee.