The two co-chairs of Bernie Sanders' 2016 presidential campaign in Massachusetts have endorsed Democratic gubernatorial candidate Jay Gonzalez.

State Reps. Mary Keefe, D- Worcester, and Paul Mark, D-Peru, announced Thursday that they are supporting Gonzalez for the Democratic nomination for governor.

Their endorsements come a day before the Democratic State Convention, which will be held Friday and Saturday in Worcester. At the convention, state Democrats will decide whether to endorse Gonzalez or his opponent Bob Massie for the nomination. Massie and Gonzalez will need support from at least 15 percent of convention delegates to get on the ballot.

Mark specifically cited Gonzalez's commitment to single-payer health care, which Mark said is the most important issue to him in the race for governor. "Jay Gonzalez is the only candidate with the right combination of practical experience in government as well as the progressive vision we need to move us forward towards a healthcare system that will work for everybody," Mark said in a statement.

Mark also compared Gonzalez to Sanders. "Like Bernie, Jay has meaningful proposals to combat some of the most pressing needs facing our state--from climate change to affordable higher education to single-payer healthcare--Jay has the passion and experience to make a real difference in peoples' lives," Mark said.

Massie also supports single-payer health care.

Keefe said she sees Gonzalez as "an inspired leader with a bold vision for Massachusetts" who is best poised to implement the recently passed overhaul of the state's criminal justice system.

Gonzalez is a former health insurance CEO and state budget chief under Gov. Deval Patrick. Massie is an environmentalist and entrepreneur.

Sanders, an independent U.S. senator from Vermont who battled with Hillary Clinton for the Democratic presidential nomination, is one of the leaders of the progressive movement within the Democratic Party.

The endorsement of Gonzalez by two prominent Sanders supporters is significant, because so far, the organization backed by Sanders has leaned toward Massie. The statewide branch of Sanders' Our Revolution declined to issue an endorsement in the race after considering whether to endorse Massie. Several local chapters of Our Revolution have come out in support of Massie.

Gonzalez has been trying to pick up support from the progressive wing of the party, and has secured support from Progressive Democrats of Massachusetts.