Jealous is vying to become the first African American to lead the state, while Madaleno, who has indicated that he plans to run for the seat but has not officially declared, would be Maryland's first openly gay governor.
Both believe they can oust popular Gov. Larry Hogan, who is seeking to become the state's first two-term Republican governor in a half century despite a potential anti-President Trump backlash.
Charly Carter, director of Maryland Working Families, said their candidacies will ensure that bread-and-butter progressive issues such as paid sick leave and a $15 minimum wage will take center stage.
"It's the best possible scenario," Carter said. With an African American and an openly gay candidate, she added, "it's not just a strong signal for underrepresented communities in Maryland, it is a strong statement across the country."
Jealous has national name recognition and expected support from across the country, including an endorsement from the group Democracy for America before he launched his candidacy last month. Madaleno, who has served in the legislature since 2003 and holds a Senate leadership position, is well known in voter-rich Montgomery County and has been one of the most outspoken Hogan critics in the past two years.
Other likely or declared candidates include Prince George's County Executive Rushern L. Baker III, U.S. Rep. John Delaney, former attorney general Doug Gansler, Baltimore County Executive Kevin Kamenetz, technology entrepreneur Alec Ross and lawyer James L. Shea.
In a May 31 email to supporters, Jealous linked his biography and record of activism with Maryland's landmark fights over the past decade to abolish the death penalty, legalize same-sex marriage and approve a version of the Dream Act, sparking criticism from a political blogger who supports Madaleno and accused Jealous of taking credit for political victories in Annapolis that were not his.
"He was not a leader in state politics," Adam Pagnucco wrote for Seventh State. "In fact, other than residency and family history, Jealous has few ties to politics and government in Maryland."
Jealous campaign manager Travis Tazelaar replied with a strong rebuke, saying Jealous was among many in Maryland who advocated for the progressive policies and played a role in getting them passed. Tazelaar included quotes from former governor Martin O'Malley (D), who described Jealous as an "indispensable part of repealing the death penalty, passing the Maryland Dream Act, ensuring civil marriage equality and expanding access to voting."
"We should be coming together as progressives to do big things in this state again," Tazelaar wrote.
When asked about the Democrat hopefuls, Larry Stafford, executive director of Progressive Maryland, said he was "just happy that we have people jockeying for the position of progressive in the race."
State Democratic leaders are reaching out to progressives in an attempt to rebuild and refocus the party following the loss of the governor's mansion and some legislative seats in 2014. As part of that effort, the party recently named Sheila Ruth, of the Baltimore County Progressive Democrats, to the new position of progressive chair for the Maryland Democratic Party Diversity Leadership Council.
Jealous and Madaleno are different in key ways.
Jealous, whose base is in Baltimore, has been a strong voice against mass incarceration, while Madaleno, who has built his political career in the Washington suburbs, has been outspoken on abortion rights. He recently sponsored legislation that made Maryland the first state in the nation that will provide money to Planned Parenthood clinics if Congress cuts their funding.
Jealous was a surrogate for Sen. Bernie Sanders (I-Vt.) during the 2016 presidential campaign, while Madaleno backed Hillary Clinton.
Progressive Maryland and Maryland Working Families said they plan to endorse in next June's gubernatorial primary, but have not decided on when that will happen.
Last month, Del. David Moon (D-Montgomery) began asking other elected officials to pledge not to endorse any gubernatorial candidates until the winter, after the filing date for the primary and some initial debates.
Moon, a self-described "aggressive progressive," said he hopes party leaders and candidates will take the time to discuss "what we can do to win the voters that stayed home and those who went for Hogan [and] getting social and economic justice while enhancing the vote."
About 20 elected officials have taken the pledge. But others have refused, saying it is better for elected officials to rally behind candidates early.
Del. Jimmy Tarlau (D), District 47A, who served as a Sanders delegate at last summer's Democratic National Convention, said he will likely support Jealous because "he's a new face" who "brings a certain amount of excitement and more of an ability to mobilize the base . . . and he's a stark alternative to Hogan."
Del. Cory V. McCray (D), District 45, another progressive state lawmaker, said he is waiting to hear what Jealous, Madaleno and the other candidates have to say.
"I just think working families are underrepresented," McCray said. "It is even hard for Democrats to talk about working-class issues."