President Trump took to Twitter early Wednesday morning to retweet dozens of posts from purported firefighters and friends and relatives of firefighters who had taken issue with an endorsement this week of Democrat Joe Biden by a major firefighters union.

Trump began a spate of Twitter activity shortly before 6 a.m. with a tweet of his own deriding the International Association of Fire Fighters as a “dues sucking union.” He then retweeted more than 70 people who voiced disappointment with the Biden endorsement.

“I’ve done more for Firefighters than this dues sucking union will ever do, and I get paid ZERO!” Trump said in his initial tweet.

Those he retweeted suggested that Trump would have been the better candidate to back and questioned the labor union’s thinking.

“It doesn’t matter who they endorse, the only person winning in 2020 is President Trump!” said one typical tweet shared by the president with his nearly 60 million followers.

Most were replying to a tweet by Dan Bongino, a former Secret Service agent and frequent commentator on Fox News, who earlier wrote on Twitter that “NONE of the Firemen I know are supporting Joe Biden for President.”

Among the accounts Trump retweeted was onewith a display name that included a vulgarity directed toward him. It wasn’t immediately clear if the Twitter user had changed it after the retweet.

Biden won the backing of the IAFF on Monday, landing the first major labor union endorsement of the 2020 White House race.

The IAFF stayed out of the 2016 election, declining to endorse Democrat Hillary Clinton in her bid against Trump.

In a video released Monday morning, Harold Schaitberger, the IAFF’s general president, left no doubt about where the union stands this time.

“Joe’s a lot like our firefighters,” Schaitberger said. “He’s a problem solver who cares deeply about America and committed to making our country better. He’s one of the staunchest advocates for working families. He knows that a strong middle class means a strong America, and we know, as president, he will stand up for all the patriotic Americans who want nothing more than to earn a decent wage, send their kids to college, have affordable health care and a decent and secure retirement.”

Biden tweeted later Monday that he “couldn’t be more proud” to have the IAFF’s backing and said he was “sick of this President badmouthing unions.”

“Labor built the middle class in this country. Minimum wage, overtime pay, the 40-hour week: they exist for all of us because unions fought for those rights. We need a President who honors them and their work,” Biden wrote.