In a feud that played out Thursday on Twitter, President Trump referred to the Senate minority leader as “Cryin’ Chuck Schumer,” who, in turn, reminded him of an initiative just launched by the first lady that calls for children to speak online with “respect.”

Trump took aim at Sen. Charles E. Schumer (D-N.Y.) in late-morning tweets, suggesting hypocrisy in the senator’s stance on the Iran nuclear deal. Trump announced the United States’s withdrawal from the 2015 pact this week, much to the dismay of some U.S. allies.

“Senator Cryin’ Chuck Schumer fought hard against the Bad Iran Deal, even going at it with President Obama, & then Voted AGAINST it!” Trump wrote. “Now he says I should not have terminated the deal — but he doesn’t really believe that!”

Trump also took a shot in the same tweet at fired FBI director James B. Comey.

Schumer did not take long to fire back and did so with just a seven-character response: “#BeBest.”

That is the name of the initiative launched this week by first lady Melania Trump, which focuses on several major issues facing children today, including social media use.

A White House website explaining that part of the initiative says, “When children learn positive online behaviors early-on, social media can be used in productive ways and can effect positive change.”

It continues: “Mrs. Trump believes that children should be both seen and heard, and it is our responsibility as adults to educate and reinforce to them that when they are using their voices — whether verbally or online — they must choose their words wisely and speak with respect and compassion.”