The American Federation of State, County and Municipal Employees (AFSCME), which represents 1.6 million public-sector workers, will stand behind the 2016 Democratic primary front-runner.

ADVERTISEMENT

"Members want a candidate who will make it easier instead of harder to join together in strong unions and stand together for wages and benefits that can sustain our families," AFSCME President Lee Saunders said in the statement obtained by CNN

"What we also heard was AFSCME members want the candidate who will be the most effective champion for working families, and who will be able to deliver a victory in this critically important election. AFSCME members believe that candidate is Hillary Clinton," he added.

“The next president will make decisions that could make or break the ability of working people across America to sustain their families."

The endorsement comes as a major blow to Democratic primary rival Sen. Bernie Sanders (I-Vt.), who has positioned himself as a populist candidate.

AFSCME is the latest big labor union to back Clinton’s strengthening White House bid.

She has also picked up support from the National Education Association, the largest teachers union in the country, as well as national plumbers and carpenters unions.

Clinton recently came out against the Trans-Pacific Partnership, a trade agreement she helped negotiate in the Obama White House.

The deal is despised by American labor unions, and Clinton's presidential primary rivals — Sanders and former Maryland Gov. Martin O'Malley — have long opposed it.

Republicans said the endorsement is a sign that Clinton has sold out to special interests.

“Hillary Clinton is now officially beholden to the big government union bosses who routinely put their special interests ahead of the hard working taxpayers," Republican National Committee (RNC) Chairman Reince Priebus said in a statement on Friday. "With their endorsement, it’s clear AFSCME is counting on Hillary Clinton to block commonsense efforts to reign in Washington’s runaway wasteful spending that is mortgaging our children’s future.”

-Updated 2:38 p.m.