Mark Kelly speaks as his wife, former U.S. Rep. Gabby Giffords, looks on during a roundtable discussion with gun violence survivors last year. Kelly said Tuesday that he’s planning to run for U.S. Senate in 2020.

When he was in Congress, John McCain acted almost as a U.S. senator at-large.

Yes, he lived in Arizona, on the occasions he was home, but his constituency seemed to go from coast to coast and border to border. We in Arizona just voted on whether we liked him every six years — and it turns out we did, despite or because of his sweeping view of his role.

You could imagine a similarly broad constituency for Mark Kelly, who announced Tuesday he is planning to run for the Democratic nomination for U.S. Senate in 2020. For 6½ years, he and his family have lived in Tucson, but clearly Kelly is a global citizen with nationwide appeal. Like McCain, he could be ours but not ours at the same time.

If he wins the Democratic nomination, Kelly is likely to be running against another Tucson resident, incumbent Republican U.S. Sen. Martha McSally, for the seat McCain occupied for more than 30 years. While McSally seemed for a time to be McCain’s heir apparent — they were both combat pilots and rock-ribbed Republicans — the similarities between McCain and Kelly seem even more striking.

As with McCain, Kelly’s reputation precedes his entry into Arizona politics. McCain was a Navy pilot famous for surviving 5½ years of imprisonment, solitary confinement and torture in North Vietnam before he moved to Arizona in 1981 and ran for the U.S. House in 1982.

Kelly was also a Naval aviator and flew combat missions in Iraq, but he became well-known to Americans as an astronaut who commanded space shuttle flights. Like McCain, who married into a prominent Arizona family, Kelly married a prominent Arizona woman — U.S. Rep. Gabrielle Giffords. That made Kelly even more famous, as he dealt with the aftermath of the assassination attempt on Giffords in 2011.

When the Star’s Joe Ferguson and I interviewed Kelly on Tuesday, I asked about his relatively short residence in Arizona. His answer echoed one by McCain, who in 1982, responded to accusations of carpetbagging by saying that having grown up in a military family, he’d moved all his life — and in fact the place he’d lived longest was Hanoi.

Kelly, who grew up in New Jersey, said, “When I left high school, I went to the U.S. Merchant Marine Academy. After that, when I graduated and started flight school, I moved to Florida. I was stationed there. Then I went to Texas, then the state of Washington and then Japan and then Maryland and then eventually stationed at NASA at the Johnson Space Center (near Houston).

“Arizona is the first place in my life that I chose to live. We picked this place. Gabby loves Arizona.”

He noted that his two daughters from his previous marriage, Claire and Claudia, also live in Arizona.

It was living here in Arizona that Kelly chose to depart from his role as a celebrity astronaut and husband, taking a stand on one of the most controversial issues of the day — gun laws. I was there in March 2013, at the northwest-side parking lot where Giffords was shot two years before, when Kelly laid out his argument for universal background checks.

“It is clear that this legislation could do a very common-sense thing, to make it more difficult for criminals and the mentally ill to have access to a firearm,” he said then.

Since then, Kelly has testified around the country, advocating for stronger gun laws while also laying claim to the idea of responsible gun ownership. When I asked him about it Tuesday, he brought up a familiar figure.

“Sen. John McCain voted for the background check bill that would require pretty much all gun owners to get a background check before buying a gun. That’s just common sense — Arizonans get that,” he said.

Indeed, McCain got in some trouble with gun-owners’ groups for that stand. But on Tuesday, Kelly seemed to be slightly de-emphasizing his stand on the issue that has been his signature for almost six years. Undoubtedly he’ll face flak for his position if he makes it to the general election.

“I probably own more firearms than your average person in this state. I’m a strong supporter of the Second Amendment. When you have 40,000 people being shot and killed every year, and another 100,000 shot and injured we’ve got to address the problem. We’ve got to look at solutions,” he said.

And when I asked Kelly about how he thinks President Trump is doing, he was surprisingly restrained for a Democrat and much different than U.S. Rep. Ruben Gallego will be if he runs for the Democratic nomination as expected.

“From my experience, as the commander of the space shuttle and in combat, you usually come up with a plan. You look at science and data to figure out what’s the right approach. I don’t see this from the White House. I don’t see a tone from the White House that I think is respectful.

“I hope to be able to represent this state not as a partisan, but as a patriot and an independent. The president and the White House — I don’t think they’re representing the middle class.”

This, of course, made me wonder how Kelly can be a representative of the middle class, given where he’s arrived in his life. He’s a well-paid public speaker, with fees likely in the tens of thousands of dollars for a single speech, as much as many Tucsonans make in a year. And he has appeared on advertisements for brands such as Breitling watches. One watch he’s advertised retails for $7,200.

When I asked about this, Kelly’s first words were “I’m a regular guy.”

He went on to describe a working-class childhood in New Jersey, in which both parents were police officers and money was scarce. Certainly it’s a long way from the life he lived there as a kid to the one he’s living now in Tucson, Arizona and the world.

It’s a journey that, if he’s elected, could even measure up to that of McCain.

Contact: tsteller@tucson.com or 807-7789. On Twitter: @senyorreporter.