State Sen. Richard Madaleno (D-Montgomery), second from left, introduces his children, Katie and Jackson, along with his husband, Mark Hodge, after officially announcing his campaign for governor of Maryland. (Katherine Frey/The Washington Post)

Maryland state Sen. Richard S. Madaleno Jr. (D-Montgomery) formally launched his campaign for governor Monday, saying his progressive track record and nearly 15 years as a state lawmaker distinguish him from others in a growing field.

“I am the only Democrat who can take on and beat Larry Hogan next November,” said Madaleno, 52, who first announced his plans to challenge the popular Republican governor at a rally for more Metro funding in May.

Other Democrats who have said they will compete in the June 2018 primary include Prince George’s County Executive Rushern L. Baker III; former NAACP president Benjamin Jealous, who recently won endorsements from Sen. Bernie Sanders (I-Vt.) and Our Revolution, the progressive group Sanders formed after his 2016 run for the Democratic presidential nomination; entrepreneur Alec Ross; and attorney James Shea.

Three other Democrats — Baltimore County Executive Kevin Kamenetz, Rep. John Delaney and former state attorney general Doug Gansler — are also weighing bids.

Madaleno, who would be Maryland’s first openly gay governor, is one of two candidates trying to win over far-left voters and carry the progressive mantle in the 2018 gubernatorial race. Both he and Jealous, who would be the state’s first African American governor, have strong social-justice records and support a $15 minimum wage.

State Sen. Richard Madaleno (D-Montgomery). (Katherine Frey/The Washington Post)

As governor, Madaleno said, he would push for universal pre­kindergarten in Maryland and larger investments in higher education “to make the dream of a college degree without debt a reality.”

Like many of his fellow Democrats, he criticized Hogan for not speaking out more forcefully against Republican plans to overhaul the Affordable Care Act. He said he would be willing to use Maryland taxpayer money to ensure that the state’s Medicaid is not diminished if Congress repeals the federal health-care law, which provided funding to expand eligibility for the program in Maryland.

By running for governor, Madaleno must forfeit his chance to run for another term in the legislature, where he is vice chair of the Senate Budget and Taxation Committee. He described his gubernatorial campaign as an “up-or-out situation.”

Madaleno worked as a legislative aide in the General Assembly before winning election to the House of Delegates in 2002 and the Senate in 2006.

He helped lead the push to legalize same-sex marriage in Maryland and sponsored legislation this year that makes Maryland the first state to guarantee Planned Parenthood will not lose funding in the state if Congress cuts off federal money for the organization.

Madaleno was joined at the campaign kickoff by his parents, his husband and their two children, along with campaign and legislative staffers and Dels. Alfred C. Carr Jr. and Jeff Waldstriecher, both Montgomery County Democrats.

He told reporters that he believes Democrats should wait until later in the primary cycle, after seeing which candidate connects with and energizes voters the most, before making endorsements. And he shrugged off the endorsement of Jealous by Sanders as relatively inconsequential in Maryland, where voters backed Hillary Clinton by a wide margin.

“I doubt I will get a lot of votes in Vermont, but then again, that’s not a high priority in this campaign,” he quipped.