Arizona Democratic Senate candidate Mark Kelly likes to say he comes from a tradition of service. 

As he reminded voters during the Oct. 6 debate against Republican incumbent Sen. Martha McSally, his parents were both police officers in West Orange, New Jersey, where he and his twin brother Scott were raised.

KELLY CLASSMATES REBUT CLAIM AZ SENATE CANDIDATE DRESSED AS HITLER IN OLD HALLOWEEN PHOTO

Kelly, 56, graduated from Mountain High School in 1982 before attending the U.S. Merchant Marine Academy for four years and receiving a Bachelor of Science in marine engineering. In 1994, Kelly received a Master of Science in aeronautical engineering from the Navy's postgraduate program.

His father, Richard, was an Army veteran in the 82nd Airborne Division prior to his career in law enforcement. 

In 1987, the now candidate became a naval aviator, serving in Japan and making deployments to the Persian Gulf in Operation Desert Storm.

In 1993, he attended the U.S. Naval Test Pilot School. His service has earned him almost two dozen military-related medals of commendation.

Three years later, NASA selected the brothers to be Space Shuttle pilots and Kelly flew his first four flights aboard the shuttle Endeavour.

Five years later, Kelly piloted the Space Shuttle Discovery -- the second "Return to Flight" mission following the loss of Columbia in 2003. This was after being successfully treated for colon cancer in 2007.

In 2008, Kelly flew his first mission as a commander and, after his final mission in 2011, Kelly announced his retirement both from NASA and the Navy.

Kelly's wife, former Arizona Democratic Congresswoman Gabrielle Giffords, was targeted in an assassination attempt at the beginning of the same year. Giffords sustained a severe traumatic brain injury from the attack. 

Mark Kelly speaks during a drive-in campaign rally at Pima Community College West in Tucson, Ariz., on Oct. 28, 2020. (Mamta Popat/Arizona Daily Star via AP)

Mark Kelly speaks during a drive-in campaign rally at Pima Community College West in Tucson, Ariz., on Oct. 28, 2020. (Mamta Popat/Arizona Daily Star via AP)

The couple now live in the southeastern city of Tucson. They have two daughters. 

Since his retirement, Kelly has authored multiple books ‒ including a biography describing Giffords' shooting in detail ‒ and has co-founded the near-space exploration company World View Enterprises.

In 2013, the couple founded the organization GIFFORDS as well as a political action committee named Americans for Responsible Solutions. The committee's mission is to support the Second Amendment while providing solutions to gun-related violence.

While Sen. McSally has told Arizonans she was the "Second Amendment senator," Kelly said he has owned guns and that the issue was personal for him.

A proponent of universal background checks, Kelly argued that stronger gun laws are "not inconsistent" with the Second Amendment.

"Our rights and traditions are so important. [The] Second Amendment is so important," he said. "But we can never let a bunch of kids in [their] classroom, you know, get killed and think there's nothing we can do about it."

Kelly announced his candidacy in February 2019, with a platform that includes plans for health care, veterans, the economy, border security and immigration, education, social justice, climate change and national security.

Kelly has expressed support for providing a public health insurance option and building on the Obama-era Affordable Care Act.

Although Kelly pledged not to accept money from corporate political action committees, McSally has blasted her opponent on the issue, calling him Senate Minority Leader Chuck Schumer's "star recruit" and giving him the Trumpian moniker "Counterfeit Kelly" for most of the debate. 

Kelly, who has led the race in the past couple of months, rejected the labels, arguing he would be more independent in Washington, D.C., than McSally.

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Demographics in the Copper State have changed with the introduction of younger voters ‒ who tend to skew toward liberals ‒ and Latinos, making the battleground an election toss-up.