The head of the nation's largest labor federation wants union priorities front and center on the 2016 campaign trail. In a speech delivered Tuesday to union activists and leaders in Washington, AFL-CIO President Richard Trumka called on presidential candidates to embrace the federation’s agenda of “raising wages,” a broad platform that includes increases in the minimum wage, investments in infrastructure and opposition to what unions deem to be corporate-friendly trade agreements such as the current incarnation of the Trans-Pacific Partnership.

“It’ll be our measuring stick throughout the entire presidential campaign,” Trumka said. “The labor movement’s doors are open to any candidate who is serious about transforming our economy with high and rising wages.”

However, the speech was short on specifics. And in practical terms, the endorsement process can be quite complex.

Individual affiliates of the federation, such as the United Steelworkers or the American Federation of State, County and Municipal Employees, generally endorse their preferred candidates during the primaries. But the AFL-CIO typically holds back its endorsement -- which requires the support of unions that represent two-thirds of the federation’s total membership -- until after the primaries. Notable exceptions include Al Gore, in October 1999, and Walter Mondale, in 1983.

The other major labor federation, Change to Win, includes the politically powerful Service Employees International Union and International Brotherhood of Teamsters. Both SEIU and the AFL-CIO played major roles in President Barack Obama’s 2008 victory and his 2012 re-election campaign.

As organized labor seeks to leave its mark on the campaign trail, state federations of the AFL-CIO will hold “raising wages” summits in each of the first four primary states: Iowa, Nevada, New Hampshire and South Carolina. The first one kicks off next month in Iowa, where former Secretary of State Hillary Clinton remains the lone Democrat to formally campaign.

Officials from major unions have expressed reservations about Clinton’s views on trade and her ties to Wall Street, but she is considered substantially less hostile to labor interests than any of her Republican counterparts.