Former NASA astronaut Mark Kelly is running for the Senate in Arizona as a member of the Democratic Party, after toying with the idea for the last couple of weeks. Kelly commanded NASA’s Space Shuttle twice, and he’s also a former Naval aviator who flew 39 combat missions in Operation Desert Storm. Now, he’s hoping to add “senator” to his résumé.

“I always knew I was going to serve this country in some way,” Kelly says in a video announcing his candidacy.

This is Kelly’s first campaign, but he has had tangential experience with politics for over a decade. He’s been married to former US Congresswoman Gabrielle Giffords (D-AZ) since 2007. Giffords, who survived a gunshot wound to the head during a mass shooting in 2011, has become a strong advocate for gun control reform, and Kelly has joined her in calling for change. Kelly and Giffords created a political action committee called Americans for Responsible Solutions that promotes legislation for gun control and helps elect lawmakers that support stricter gun laws. “One thing I realized early on, you know, was that Gabby needed me to help her through this,” Kelly says. “She needed an advocate. And the thing I have to do for my wife is to be able to think clearly and make good decisions.”

Kelly, who is also a former engineer, suggested that climate change will be one focus of his campaign, as warmer weather will lead to more droughts in Arizona. “We’ve seen this retreat from science and data and facts, and if we don’t take these issues seriously, we can’t solve these problems,” Kelly says in the video. “We’re going to need to bring people together from all parts of the state and all walks of life.”

Though Kelly flew on four Space Shuttle missions, he may be best known for participating in NASA’s recent Twin Study. Kelly has an identical twin, Scott Kelly, who was also a NASA astronaut. From 2015 to 2016, Scott spent nearly a year aboard the International Space Station, while Mark stayed on the ground. The goal was to see how long-duration spaceflight may affect the human body by comparing the identical twins to one another. The research found that Scott’s gut bacteria, chromosomes, and gene expressions all changed while in space when compared to the biology of his brother Mark.

A few other astronauts in US history have turned to politics after they fly. The most notable example is former astronaut John Glenn, the first American to orbit the Earth. He served as a Democratic senator for Ohio from 1974 to 1999. Glenn even flew on the Space Shuttle in 1998 during his tenure in the Senate. Moon walker Harrison “Jack” Schmitt, who flew on Apollo 17, also became a senator in New Mexico in 1976.

Additionally, there have been a few politicians who have gone into space after being elected to office. Edwin “Jake” Garn, a former Utah senator and a retired Navy pilot, leveraged his position as head of the subcommittee that funds NASA to fly as a payload specialist aboard the Space Shuttle in 1985. Bill Nelson, who lost his Florida Senate seat in the 2018 midterm election, flew on the Shuttle in 1986 while in Congress.

If he wins the Democratic primary, Kelly will face Sen. Martha McSally (R-AZ) in the Arizona special election next year. McSally narrowly lost in the general election last year against now Sen. Kyrsten Sinema (D-AZ) and is serving in Congress after being appointed to replace former Sen. John McCain (R-AZ) by Arizona Gov. Doug Ducey.

Makena Kelly contributed to this report.