Space shuttle Endeavour crew Commander Mark Kelly on the tarmac at Kennedy Space Center last month. (Joe Raedle/ Getty Images)

Senator Mark Kelly?

That’s the question in political circles this week. The minute Kelly, 47, announced his retirement from the Navy and NASA Tuesday, the behind-the-scenes speculation that’s been brewing for weeks went public: Will the husband of Rep. Gabrielle Giffords run for office himself?

One of Arizona’s Senate seats is open in 2012, thanks to the retirement of Jon Kyl. Giffords has been polling way ahead of any other Democratic candidate, even amid uncertainty about her recovery. Now the name of her Gulf War vet-turned-astronaut husband is in play.

“Gabrielle is working hard every day on her mission of recovery. I want to be by her side,” Kelly wrote on Facebook Tuesday. Though he has not previously expressed an interest in elected office, he left an intriguing hint: “After some time off, I will look at new opportunities and am hopeful that one day I will again serve our country.”

Giffords and Kelly pose together in an undated photo. (Anonymous/AP)

Much will depend on Gifford’s recovery, though no decision has to be made until next year. She has three options, notes our colleague Chris Cillizza: Run for re-election to her House seat, run for the open Senate seat — or resign from office, which would make Kelly the favorite son and logical successor. If he’s interested.

Kelly couldn’t be reached for comment Wednesday; a NASA spokeswoman said he’s not giving interviews on the topic.