AFL-CIO President Richard Trumka told Yahoo Finance on Wednesday that the support of the U.S.'s largest federation of labor unions has "yet to be earned" by the Democratic presidential hopefuls.

Even as the Democratic field narrowed after Super Tuesday, the AFL-CIO is "still evaluating" and "still asking the tough questions,” Trumka said.

The AFL-CIO represents about 12.5 million workers, and the group’s endorsement is hotly coveted by candidates running for office. Last election cycle, the union backed Democrat Hillary Clinton, but Trumka suggested that this time around, its endorsement remains in play.

"When you convince us that you are going to fight on our behalf, that you're going to change the rules on behalf of working people, we will be out in full force, we'll mobilize, and we'll help get that person elected," Trumka said in an interview on “On The Move.”

According to the union chief, the AFL-CIO's members are looking at "kitchen table economics" and candidates who can deliver in areas such as wages, health care, retirement and job security.

"They're looking for their children to be able to get a good education and do better than they are in life. And they're looking for candidates that are going to be pro-worker and actually change the rules of the game so that workers can get ahead, not just with lip service,” he said.

“They want to be convinced that you're serious about changing those rules so that we can all get a better chance at this and more opportunity," Trumka added.

Next week, the AFL-CIO will host a forum that will include Sen. Bernie Sanders, former Vice President Joe Biden — who is now considered the frontrunner — and Sen. Elizabeth Warren.

"Unlike other forums that are existing out there, we're going to have our members asking questions of those candidates, and they'll get a chance to respond. And, our members will know who is doing the old two shoe and who is giving a straight honest answer,” Trumka told Yahoo Finance.

“It will be a chance to earn the support of our members in a big way,” he added.

Julia La Roche is a Correspondent at Yahoo Finance. Follow her on Twitter.



Read the latest financial and business news from Yahoo Finance

Follow Yahoo Finance on Twitter, Facebook, Instagram, Flipboard, SmartNews, LinkedIn, YouTube, and reddit.