New Jersey Gov. Chris Christie, struggling to gain traction in a crowded 2016 GOP presidential field, said Sunday that a national teachers union deserves a “punch in the face” and called it the “single most destructive force in public education.” Christie said the union cares only about higher wages and benefits and not about children.

Christie, who has long made teachers unions a favorite foil, made the comments on CNN’s “State of the Union” in response to host Jake Tapper, who noted that Christie has said that he confronts bullies by punching them in the face. “At the national level, who deserves a punch in the face?” Tapper asked.

Without missing a beat, Christie said: “Oh the national teachers union, who has already endorsed Hillary Clinton 16, 17 months before the election.”

Christie was referring to the American Federation of Teachers, the second-largest teachers union, which became the first national labor union to make an endorsement in the 2016 race when it gave its backing to Clinton on July 11. The largest union, the National Education Association, has not yet made an endorsement.

Christie said the AFT was “not for education for our children. They’re for greater membership, greater benefits, greater pay for their members. And they are the single most destructive force in public education in America. I have been saying that since 2009. I have got the scars to show it. But I’m never going to stop saying it, because they never change their stripes.”

Randi Weingarten, the AFT president and a close Clinton ally, responded with a statement Monday.

“Chris Christie has issues – from reneging on his promise to fix pensions to his state’s fiscal standing facing near junk bond status,” Weingarten said. “But the biggest issue is he’s a bully and has anger management problems. That he would threaten to punch teachers in the face – mostly women seeking to help children meet their potential and achieve their dreams — promotes a culture of violence and underscores why he lacks the temperament and emotional skills to be president, or serve in any leadership capacity. It’s a sad day in the life of our nation to see a candidate threaten violence to gain political favor.”

Christie has long tangled with public employee unions but has a particularly fraught relationship with teachers unions, frequently railing against their pensions and health care benefits. He has called the unions “political thugs,” and he has had several public confrontations with individual teachers, captured on video and replayed on YouTube or cell phone images shared widely on social media .

In 2013, after Christie delivered a speech at a VFW hall during his campaign for re-election to a second term as governor, middle school teacher Melissa Tomlinson asked Christie, “Why are you portraying our schools as failure factories?” He wagged a finger at her and said: “What do you want? I’m tired of you people,” according to Tomlinson.

Recent polls put Christie toward the bottom of the Republican field in the 2016 presidential contest, with about 3 percent of likely GOP voters in his corner.