Democratic front-runner Hillary Clinton on Thursday scored a major endorsement from the Service Employees International Union (SEIU), a group that represents more than 1.9 million workers in the United States and Canada.

The SEIU backing marks the latest indication that the former secretary of state is consolidating support among, what the New York Times called, the "institutional pillars" of the Democratic Party. The union's national board voted overwhelmingly to back the 68-year-old candidate, and Mary Kay Henry, its president, told the newspaper that the workers it represents "believe (that Clinton) is going to fight like hell for our agenda."

"Hillary Clinton has proven she will fight, deliver and win for working families," Henry argued, according to Time magazine. "SEIU members and working families across America are part of a growing movement to build a better future for their families, and Hillary Clinton will support and stand with them."

The endorsement is a blow to the presidential campaigns of Clinton's Democratic rivals, Vermont Sen. Bernie Sanders and former Maryland Gov. Martin O'Malley. It comes after O'Malley criticized the former New York senator for only supporting an increase of the overall minimum wage to $12 per hour and not the $15 demanded by the 52-year-old former governor and, incidentally, the SEIU, the New York Times pointed out.

"We don't see it as a contradiction," Henry said about that discrepancy, arguing that Clinton had encouraged her to keep up the pressure to push the wage to that level. "She said to me, 'Listen, SEIU and 'Fight for $15' should continue to push the whole nation; we all need to get to $15,'" she recalled a conversation with the candidate.

Sanders, meanwhile, has won the endorsement of some other important, though smaller, unions in the United States, Time recalled. The 74-year-old senator can count on support from the American Postal Workers Union and the National Nurses United, which each have about 200,000 members, the magazine noted.