(Bloomberg) -- Mark Kelly, the retired astronaut and husband of former Democratic Representative Gabrielle Giffords, will run for the Senate seat from Arizona formerly held by John McCain, setting up a potentially competitive 2020 race in an increasingly purple state.

“My next mission... #FullSpeedAhead #ForArizona,” Kelly said in a post on Twitter. He also posts a video featuring images of his wife right after an assassination attempt and pictures with his identical twin, who also became an astronaut.

“I care about people, I care about the state of Arizona, I care about this nation, so because of that, I’ve decided that I’m launching the campaign for the United States Senate,” Kelly said in the video.

Kelly likely would be a strong candidate to try to flip the Senate seat to Democrats in a state where the party has had recent successes. His nomination probably would set up a general election showdown with Republican U.S. Representative Martha McSally and could help improve the performance in Arizona of whomever Democrats nominate in the 2020 presidential race.

Arizona Governor Doug Ducey announced Dec. 18 that he was appointing McSally to fill the vacancy created by the August death of McCain, a Republican icon who had held the seat since 1987. Former GOP Senator Jon Kyl temporarily took the post after McCain’s death.

McSally, a blunt-talking former Air Force combat pilot, ran unsuccessfully for Arizona’s other Senate seat in November, losing narrowly to Democrat Kyrsten Sinema. McSally is a favorite of Senate leadership including Majority Leader Mitch McConnell of Kentucky, who had urged her appointment.

(Updates with race background starting in fourth paragraph.)

To contact the reporters on this story: Kasia Klimasinska in Washington at kklimasinska@bloomberg.net;Kathleen Hunter in London at khunter9@bloomberg.net

To contact the editors responsible for this story: Kasia Klimasinska at kklimasinska@bloomberg.net, John Hughes, Elizabeth Wasserman

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