The FBI in 2025 shut down an inquiry into allegations that a political adviser to Sen. Susan Collins had participated in a scheme to funnel illegal campaign contributions from a defense contractor seeking lucrative federal contracts, current and former officials said.

The bureau began investigating the matter under the Biden administration, after Martin Kao, the CEO of Navatek, a military contractor in Hawaii, said he had discussed circumventing campaign finance laws with a political adviser to Collins, R-Maine. Kao is now serving an 87-month prison sentence for wire fraud, money laundering and bank fraud, some of which related to a separate scheme to defraud the government of pandemic aid money.

The inquiry was closed under the Trump administration last year because senior bureau officials questioned the veracity of Kao’s account, which he began offering around the time he pleaded guilty in 2022.

Current and former officials familiar with the investigation, who spoke on the condition of anonymity to describe a sensitive inquiry, said agents did not uncover much evidence to corroborate Kao’s claims against the senator and her advisers, including Scott Reed, a fundraiser for Collins, 73. But they acknowledged that it was possible more could have surfaced if the investigation had developed further.

The disclosure of the inquiry and its closing came in the final weeks of a midterm election in which Collins is in a tight race that could help decide control of the Senate. It prompted accusations that the FBI’s decision to shut down the investigation last year was influenced by political considerations — safeguarding a critical seat that could decide which party controls the Senate.

Annie Clark, Collins’ deputy chief of staff, described the allegations against the senator and her advisers as “categorically false.” In a lengthy social media post Tuesday morning, she said that her campaign “cooperated fully with the FBI throughout the investigation, producing all of the documents it requested and serving as fact witnesses in official settings.”

“As Martin Kao was awaiting sentencing, he began making outlandish charges about the Collins office, deflecting blame from himself and placing it on Senator Collins,” she wrote, adding, “The FBI and the Court obviously did not believe Kao.”

In an email to ProPublica, which earlier reported the nature of the investigation, Clark added that the campaign ultimately returned the money.

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This article originally appeared in The New York Times.

By Glenn Thrush, Alan Feuer and Devlin Barrett/Tierney L. Cross
c. 2026 The New York Times Company