PHOENIX — Mark Kelly, the retired astronaut and husband of former Congresswoman Gabby Giffords, is running for late John McCain's Senate seat.

A video was posted on Kelly's website Tuesday, showing that his run for Senate in Arizona is his "next mission."

In addition to being a NASA astronaut, 54-year-old Kelly was also a U.S. Navy Combat pilot and engineer.

Kelly is a top Democratic recruit to challenge Republican Sen. Martha McSally, who was appointed to the seat late last year. The race is widely expected to be one of the most closely contested Senate races of the 2020 election.

Kelly has never held elected office but became a visible advocate for gun control after his wife was shot.

Gabby was seriously injured when she was shot in the head during a Tucson constituent event in 2011 that left six people dead and others wounded.

According to his website, the couple co-founded an organization called “GIFFORDS” that unites “Americans of all stripes to reduce gun violence and make our communities safer.”

They now live in Tucson.

Gov. Doug Ducey appointed McSally to the vacant Senate seat after his first appointee, former Sen. Jon Kyl, resigned after only a few months in office.

The seat is a top target for Democrats because McSally just lost a Senate race in November and Democrats posted a strong showing in the November election, winning three statewide contests and picking up legislative and congressional seats.

The 2020 election will decide who finishes the last two years of McCain's term. The winner would have to run again for a full six-year term in 2022.

U.S. Rep. Ruben Gallego of Phoenix is also considering a Senate run, which would likely set up a tough fight for the Democratic nomination.

Former Arizona Attorney General Grant Woods, a lifelong Republican who became a Democrat and a fierce critic of Trump, announced last week that he won't run, saying he didn't want to fight in a contested Democratic primary.

