New York City Mayor Bill de BlasioBill de Blasio2020 Democrats join striking McDonald's workers Biden only Democrat with strong positive favorability numbers: poll CNN forces de Blasio to watch late-night comics ridicule him MORE (D) again feuded with President TrumpDonald John TrumpNASA exec leading moon mission quits weeks after appointment The Hill's Morning Report — After contentious week, Trump heads for Japan Frustration boils over with Senate's 'legislative graveyard' MORE on Friday, referring to the president as "Con Don" and calling him "very low energy." 

De Blasio launched his presidential campaign on Thursday with sharp words against fellow New Yorker Trump, with whom he has frequently feuded as mayor.

"In the course of this campaign, we’re going to talk about what working people need and how their government should be on their side. Right now, the federal government is not on the side of working people. And that’s because Donald Trump is playing a big con on America. I call him 'Con Don,'" de Blasio said during an appearance on ABC's Good Morning America on Thursday, soon after launching his campaign.

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It didn’t take long for Trump to respond. Hours later, he fired back in a video posted on Twitter, saying de Blasio is a "joke" while also calling him "the worst Mayor in the history of New York City." 

De Blasio kept up his own insults against Trump on Friday, during an appearance on MSNBC's "Morning Joe."

“Con Don himself not only tweeted at me, he created his own video,” de Blasio cracked. “I was very impressed."

De Blasio also called Trump “very low energy” and a “bully.” 

Trump has frequently used insulting nicknames against his rivals, including calling former Florida Gov. Jeb Bush "low energy" during the 2016 Republican primary.

 

“There’s nothing about Donald Trump that surprises me, there’s nothing about him that intimidates me,” de Blasio said on "Morning Joe."

“If you’re going to take on Donald Trump, it sure helps to be able to fight back and understand how to deal with him,” de Blasio said.

“I think it’s about knowing how to take on the bully,” de Blasio said. “Go right at him and take him down.”