Representative Christopher Collins, a Republican from New York, exits federal court in New York, on Wednesday, Aug. 8, 2018.

Rep. Chris Collins, R-N.Y., is set to change his not-guilty plea on federal insider trading charges on Tuesday, court documents show.

Collins, 69, was the first congressman to back Donald Trump during the 2016 campaign. He was arrested in August 2018 on charges that he shared private information related to Australian biotech company Innate Immunotherapeutics, where he served as a board member.

He was accused of frantically calling his son, Cameron Collins, from the White House lawn to share information about a failed drug trial. His son and others are accused of then selling their stock based on that tip before the trial results became public.

Federal prosecutors in New York had narrowed the charges against Collins last month. They explained in an Aug. 6 letter to Judge Vernon Broderick that the new indictment against Collins "removes references to conduct" that Collins "contends (or could contend) is protected by the Speech and Debate Clause" of the U.S. Constitution.

Collins and two alleged co-conspirators in the case, including his son, pleaded not guilty to the revised indictment on Sept. 12. But court filings made public Monday show Collins and his son — as well as Stephen Zarsky, the father of his son's fiancee — will change their pleas this week.

Collins' change-of-plea hearing is scheduled for 3 p.m. Tuesday in Manhattan federal court before Broderick. Another hearing for Zarsky and Cameron Collins is set for 2 p.m. Thursday.

Shortly after his arrest, Collins suspended his reelection campaign for New York's 27th Congressional District. But just over a month later, Collins restarted the campaign — and won in the 2018 midterms.

"I will work to ensure the 27th Congressional District remains in Republican hands, while I fight to clear my good name in the court," he said in a statement at the time he revived his congressional bid.

Collins' district voted more solidly for Trump in 2016 than any other district in New York.