After President Trump’s first term, many of his loyalists found new perches by setting up advocacy groups to promote conservative policies. Kash Patel’s was not like the rest.

Other former Trump staff members used the millions of dollars they raised to build a second Trump administration in waiting. Their nonprofits had names like America First Policy Institute or the Center for Renewing America.

Mr. Patel’s charity was called the Kash Foundation. And its greatest cause often seemed to be the promotion of Mr. Patel himself.

Mr. Patel, now Mr. Trump’s nominee for F.B.I. director, used his charity to promote his media appearances, hawk his books and sell T-shirts with his name on them — made by a company he co-owned. His charity did make donations to those in need, including veterans, but also to Jan. 6 rioters and other Trump allies. But its most recent tax filings showed it spent more on “advertising and promotion” than on charitable giving. By law, charities must serve the public good and not the private interests of their leaders.

“It looks like the charity is fundamentally about making sure merchandise promoting Kash Patel gets sold into the world,” said Philip Hackney, a former I.R.S. lawyer who now teaches nonprofit law at the University of Pittsburgh. He said that the I.R.S. only enforced this rule in extreme cases, but that Mr. Patel’s use of his nonprofit for self-promotion raised questions.

Mr. Hackney said that if Mr. Patel wanted to set up a site to promote his views and sell his name-branded gear, “run it with your own money — not with your charity.”