MADISON, Wis. — GOP U.S. Senate candidate Kevin Nicholson has disclosed doing consulting work for more than two dozen companies since 2016, and half of them are financial firms.

The Wisconsin State Journal reported Saturday that Nicholson’s disclosure to the Senate Ethics Committee helps fill in a key piece of his biography: his business career as a management consultant. He’s currently with the Chicago firm ghSMART.

Nicholson is vying with state Sen. Leah Vukmir for the GOP nomination to face Democratic U.S. Sen. Tammy Baldwin in November. He has made his business career, alongside his military service in the wars in Iraq and Afghanistan, central to his candidacy.

Half of the 26 clients Nicholson disclosed are financial firms. They include private equity firms such as New York-based American Securities and Boston-based Berkshire Partners, and investment advisers such as Los Angeles-based Ares Management. The others include manufacturing, technology, IT, oil and gas, and self-storage companies.

Nicholson had declined previously to name his consulting clients. His spokesman, Brandon Moody, said Nicholson decided to release his client list Friday following guidance from the ethics committee.

Government watchdog groups said it’s good that Nicholson revealed which companies have paid him during the last two years. They said it would help identify possible conflicts of interest should Nicholson win office.

Nicholson’s clients include “some big-name companies that have a history of engagement with the federal government and could potentially stand to benefit by having someone like Nicholson — whom they’ve had a working business relationship with — in a position of power,” said Alex Baumgart, a researcher at the nonpartisan Center for Responsive Politics.

U.S. Senate candidates are required to disclose to committee all sources of more than $5,000 compensation in the two preceding calendar years and the current year. Moody said a stumbling block to disclosing clients earlier was that ghSMART signs agreements with its clients to keep their work confidential. Nicholson previously told the committee he collected $362,417 in salary and $808,180 in commissions from ghSMART since 2016.

Democratic Party of Wisconsin spokesman Brad Bainum said Nicholson should go beyond the disclosure requirements and offer up more about the nature of his work for the companies.

Information from: Wisconsin State Journal,