Madaleno said the $10.10 minimum, which takes effect in July under legislation signed by former governor Martin O'Malley (D), is not keeping up with inflation and leaves too many workers struggling to make ends meet.
"No one working full time should live in poverty," said Madaleno, one of seven Democrats vying to challenge Gov. Larry Hogan (R) in the 2018 election.
"This is a critical step in restoring fairness to the working families of our state," he said.
Another Democrat running for governor in 2018, former NAACP president Ben Jealous, has made raising the minimum wage to $15 part of his campaign platform. And a third candidate, attorney James L. Shea, attended Monday's news conference in Annapolis announcing the bill and said he supported a $15 hourly minimum, as well.
The crowd of about 200 supporters included at least 15 state lawmakers.
California and New York state have passed legislation phasing in a $15 minimum wage over time. The District approved a similar measure in 2016, and Montgomery County did the same in November. But neighboring Prince George's County has declined to support a $15 minimum wage, saying county businesses would be placed at a competitive disadvantage unless the higher pay scale was implemented statewide.
Maryland's legislature debated a $15 minimum wage bill in each of the past two sessions, but those bills never got out of committee. Advocates said they hope this year's campaign will be buoyed by the recent passage of sick-leave legislation in Maryland, which is another top priority for progressives.
In Virginia, Gov. Ralph Northam (D) and his Democratic primary rival, Tom Perriello, called for a $15 minimum wage during the 2017 primary campaign.
Hettleman said the Maryland bill is "about fairness and equity" and would help address wage stagnation and growing wealth inequality in Maryland.
"A decent wage for a day's work is at the very core of America's promise to its workers," she said.
The Service Employees International Union, which has endorsed Jealous for governor, and the immigrant-advocacy group CASA are backing the bill, which supporters said would affect hundreds of thousands of workers.