Federal investigators terminated a case involving a political adviser to the Republican senator after allegations of unlawful fund transfers from a military firm. The inquiry examined whether Martin Kao, chief executive of the Hawaii-based Navatek, discussed ways to circumvent campaign finance laws with the adviser to secure lucrative federal contracts.

The FBI began the investigation under the Biden administration but shuttered the inquiry in 2025. A spokesperson for Senator Susan Collins' office stated that federal agents previously concluded that suggestions of wrongdoing by the campaign were totally false. Kao received prison sentences of 7 and 3 years in 2025 for fraud, money laundering, and false submissions to the FEC.