Hillary Rodham Clinton has won the endorsement of a powerful union representing an array of government workers. 

The 1.6 million-member American Federation of State, County and Municipal Employees announced its support of Clinton on Friday. 

The union's president, Lee Saunders, says Clinton would be the "most effective champion for working families." 

Clinton received AFSCME's endorsement in the fall of 2007 and its backing was sought by both Clinton and Vermont Sen. Bernie Sanders. 

The union was influential in President Bill Clinton's two terms in the White House during the 1990s and plays a significant role in Iowa, the home of the nation's first presidential caucus. 

Republican National Committee chairman Reince Priebus says the endorsement showed Clinton is "now officially beholden to the big government union bosses."