Montana GOP Senate candidate Tim Sheehy failed to disclose his role at the Property and Environment Research Center, a property rights and environmental research nonprofit that has a history of advocating for privatizing Americas federal lands and rolling back environmental laws including the Endangered Species Act .

Sheehy, a former Navy SEAL and wealthy businessman who is running against three-term incumbent Sen. Jon Tester (D-Mont.), joined PERCs board in 2022, according to the organizations filings with the IRS. But he failed to include his position at the think tank in his campaign financial disclosure, in violation of Senate rules, HuffPost has learned.

Public lands have emerged as a key issue in the race, with Tester painting Sheehy as a threat to their future and the Montana way of life. Sheehys failure to disclose his work at PERC could further complicate his already messy messaging on public lands policy.

Sheehy did report being a board director at other nonprofits; however, PERC does not appear on his disclosure form.

Sheehys campaign told HuffPost that Sheehy stepped down from the board prior to entering the Senate race last June. Asked why he didnt disclose his role at PERC, campaign spokesperson Katie Martin said, This omission was an oversight. We are working on amending the report.

Senate rules require candidates to report both paid and unpaid positions held in the two years prior to their candidacy at any business enterprise, nonprofit organization, labor organization or educational institution.

PERC confirmed that Sheehy left its board before announcing his campaign last year. But as of Wednesday, PERCs website still listed Sheehy as a board member.

Tim was elected to the board in Fall 2022 due to his relevant background as a successful local entrepreneur in the area of forest health, wildfires, and ranching, all conservation issues we are engaged in, Kat Dwyer, the organizations marketing and media manager, said in an email.