Meet Martin O'Malley: Everything You Need to Know (and Probably Didn’t Know) About the 2016 Democratic Presidential Candidate

And a few things you probably didn't know.

— -- Name: Martin Joseph O'Malley

Party: Democratic

What he does: O’Malley became a visiting professor at the Johns Hopkins University Carey Business School in January 2015 after finishing two terms as governor of Maryland.

What he used to do: As Maryland’s governor, O’Malley ushered in a wide range of liberal policies, including same-sex marriage, gun control and a law offering in-state tuition to undocumented immigrants. Prior to serving as governor, he was the mayor of Baltimore for two terms and was on the Baltimore City Council. In 2014, he was inducted into the Irish American Hall of Fame.

Declared as a candidate: May 30, 2015 in Baltimore, Maryland.

In his own words: "Leadership is about making the right decision and the best decision before sometimes it becomes entirely popular. I believe that we are best as a party when we lead with our principles and not according to the polls.”

Breakout moment into politics: Relatively unknown at the time, O’Malley surprised his party in 1999 when he stood on a street corner in one of Baltimore’s toughest neighborhoods and announced his long-shot run for mayor in a majority African-American city. He promised “zero-tolerance” policing, and once elected he instituted a data-driven program to analyze and cut crime. “Because things that get measured are things that get done,” he often says. In 2002, Esquire featured O’Malley on its cover as “the best young mayor in America.”

One thing you need to know to understand him: Even as governor, he continued to sing and play his guitar with his Celtic rock band in popular Baltimore bars.

Family tree: When he was working as a prosecutor and his wife, Katie, was a law student, O’Malley invited her to come see his band play, according to a campaign spokeswoman, who added, “Katie says that the rest was history.” The two were married in Baltimore in 1990. Katie is now a district court judge. They have four children: Grace, Tara, William and Jack.

How he grew up: “The two things in our household that we'd never dream of skipping were an election and mass,” O’Malley, 52, said in an interview with Baltimore magazine. He was one of six children. His father was a U.S. Attorney for the District of Columbia and, in 1987, his mother, Barbara, took a job as a receptionist for Democratic Maryland Sen. Barbara Mikulski. Three decades later, at 87, his mother still answers phones for the senator on Capitol Hill.

Education: He graduated from Catholic University in Washington, D.C., in 1985 and earned his law degree from the University of Maryland in 1988.

Claim to fame: O’Malley is rumored to have inspired the television character Tommy Carcetti, the young and ambitious mayor in the HBO show “The Wire,” although show creator David Simon maintains that several politicians influenced the character.

Also known for: Polar bear plunges. The former governor apparently doesn’t mind icy water. He has participated in many freezing dips for charity, including this one in 2009 in Baltimore with Ravens QB Joe Flacco.

Other possible baggage: O’Malley’s tough-on-crime stance has come under criticism lately, as Baltimore reels from the death of African-American Freddie Gray at the hands of police. While violent crime in Baltimore did fall dramatically under O’Malley, in 2010 the city paid $870,000 in a major settlement after the ACLU and NAACP joined a lawsuit alleging Baltimore police arrested thousands “without probable cause.”

What he has said about the race: “I think that our country always benefits from new leadership and new perspectives,” O’Malley told George Stephanopoulos on ABC’s This Week in March. “Let's be honest here, the presidency of the United States is not some crown to be passed between two families. It is an awesome and sacred trust to be earned and exercised on behalf of the American people.”

Might have wished for a do-over: Maryland had an exceptionally botched rollout of its health care exchange under O’Malley’s tenure, forcing the state to work with insurers to retroactively provide coverage to residents who had to deal with the glitch-ridden site. The problems bogged down O’Malley’s lieutenant governor and would-be heir, Anthony Brown, as he ran (unsuccessfully) for governor.