Hours before the first Democratic debate Tuesday, U.S. Sen. Bernie Sanders' campaign announced that the National Union of Healthcare Workers, a group comprised of 11,000 healthcare worker members in hospitals, nursing homes and clinics throughout California, has endorsed the candidate. The Vermont senator has surged to a strong second place in polls around the country by pushing a populist message and supporting unions.

"As a democratic, member-led union, I am grateful for the support of the National Union of Healthcare Workers," Sanders said in a press release announcing the support. "With their support and the support of hundreds of thousands of union members across the country, we are building a political revolution that will transform American politics."

The endorsement comes days after Sanders received his first congressional endorsement of the campaign from Rep. Raúl Grijalva on Friday in Tucson, Arizona. The candidate also has a long list of celebrity endorsements, including Danny DeVito, Margaret Cho and Cornel West.

“He’s grateful for their endorsements and we are actively building our collaborations. I think it’s a testament to the fire that the senator has started throughout the country,” Symone Sanders, Sanders’ press secretary, told the International Business Times. “Hundreds of thousands of union workers -- from various unions -- are standing up and saying ‘we want to stand with Bernie Sanders.’”

In averages of national polls aggregated by Real Clear Politics, Sanders trails former Secretary of State Hillary Clinton by 18.2 points, however he does much better in early nominating states like Iowa and New Hampshire. He trails by 11.7 points in Iowa, a drop from mid-September when the two were neck-and-neck. In New Hampshire, however, Sanders is beating Clinton by 9.2 points.

The first Democratic primary debate is Tuesday evening at 8:30 p.m. EST. Sanders and Clinton will share the stage with three other contestants: former Maryland Gov. Martin O’Malley, former Rhode Island Gov. Lincoln Chafee and former Virginia Sen. Jim Webb.

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