(WASHINGTON) — Cliff Sims, a former aide to President Donald Trump, who sued the president after writing a brutal tell-all book about his time in the Trump White House called “Team of Vipers”, is back on the Trump team, serving an important role overseeing speechwriting for the upcoming Republican National Convention.

Sims is not only supervising speech writing for the convention, but multiple sources tell ABC News he is also spearheading the efforts for remarks by the president’s children, including Donald Trump Jr. and Tiffany Trump.

Trump Jr. told ABC News that “Cliff is a staunch supporter of my father and his America First agenda. He fought to elect President Trump on the 2016 campaign and has done a terrific job as Alabama co-chair of Trump Victory this year.” Trump Jr. added, “I’m excited that he’s now working with the convention team to help make this year’s RNC a gigantic success.”

Sims’ return has also been welcomed inside the White House he described last year as a “team of vipers.”

“Cliff has been an outspoken supporter of the President and a resource for the administration since the beginning,” a senior White House official told ABC News. “He has a real talent for communicating the President’s message and vision, and so it was a no-brainer for the political team to turn to him for a helping hand with the convention speakers.”

It’s quite a turn of events for Sims, who served as special assistant to the president and director of White House message strategy until 2018.

The publication early last year of “Team of Vipers,” which became a bestseller and portrayed the Trump White House as a nest of infighting, backstabbing and intrigue, set off a series of harsh attacks from the president and his allies, who accused Sims of violating a non-disclosure agreement. In response, Sims actually sued the president, accusing him of attempting to violate his first amendment rights.

“A low level staffer that I hardly knew named Cliff Sims wrote yet another boring book based on made up stories and fiction,” Trump tweeted shortly after Sims book was published. “He pretended to be an insider when in fact he was nothing more than a gofer.”

Sims quietly dropped his lawsuit last year and although he painted a harshly negative portrait of many who served the president, his book was generally positive and admiring of Trump himself.

The White House said that Sims had been fired from his role; however, Sims refuted that claim and said he resigned to pursue a different job with the State Department.

Sims told George Stephanopoulos on “Good Morning America” in 2019, “In a tough environment, people usually come together, create this kind of bunk room mentality where it’s you against everyone else. That just didn’t happen in the White House. I thought there may be an opportunity to do that at [the] State [department].

Acting Director of National Intelligence Richard Grenell said he found Sims was always loyal to the president.

“I relied on Cliff during my confirmation and I regularly sought his advice throughout my multiple roles in the Administration. I’ve always found him to be loyal to President Trump and a great strategist,” said Grenell.

Other names familiar to Trump working behind the scenes on the convention include two former “Apprentice” producers, sources confirm to ABC News.

Sadoux Kim, a former employee of “Apprentice” creator Mark Burnett, is a lead consultant on the convention’s production and has been heading meetings leading up to this week, sources said. And Chuck LaBella, a ex-NBC entertainment executive who helped produce “The Comedy Central Roast of Donald Trump,” is also on the convention payroll, according to FEC filings.

The news of Kim and Labella was first reported by The New York Times.

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