The Conservative Partnership Institute, a nonprofit whose funding skyrocketed after it became a nerve center for President Donald J. Trump’s allies in Washington, has paid at least $3.2 million since the start of 2021 to corporations led by its own leaders or their relatives, records show.

In its most recent tax filings, the nonprofit’s three highest-paid contractors were all connected to insiders.

One was led by the institute’s president, Edward Corrigan, and another by its chief operating officer. At a third contractor, the board members included the group’s senior legal fellow Cleta Mitchell, a lawyer who supported Mr. Trump’s efforts to overturn the 2020 election.

Last year, the Conservative Partnership Institute hired a fourth company connected to an insider: a fund-raising firm run by Mr. Corrigan’s brother, Patrick Corrigan. Public filings show the company received a contract three weeks before the firm was legally formed.

The Conservative Partnership Institute applied to the Internal Revenue Service as a tax-exempt nonprofit, and the agency approved. That means donations to the group are tax deductible, like gifts to a food bank or the American Red Cross. It also means that, by law, its money must serve the public good rather than private interests.

The nonprofit has pushed those limits by entwining itself with only one faction of American politics. It pays high salaries to some of Mr. Trump’s former officials, hosts retreats for Republican lawmakers at a rural compound and funds efforts to vet people and ideas for a second Trump term.