Washington • With Sen. Orrin Hatch’s pending retirement, friends and supporters are ramping up efforts to raise money for a center in his name to house his decades of papers, train new leaders and offer a forum for policy discussions.

But who is funding the multimillion-dollar effort is likely to remain shrouded in mystery.

The Orrin G. Hatch Foundation had raised, according to its most recent tax filing, nearly $6 million toward building a center at one of Utah’s universities, and supporters are eyeing an eventual haul that could top $100 million.

But the nonprofit doesn’t have to list its donors.

Companies that lobby the Senate are legally required to disclose their donations, but some don’t. In fact, an analysis of Senate records shows less than a half million in donations have been publicly disclosed by companies and lobbyists pushing congressional action. That’s not even a tenth of the money the foundation has raised.

As chairman of the powerful Senate Finance Committee, Hatch oversees a broad range of key policy issues from health care to the tax code and Wall Street, among others. And government watchdogs say donors to his foundation could be currying favor with contributions that may never be made public.

Just because we don’t know, doesn’t mean Hatch doesn’t know,” says Melanie Sloan, a senior adviser at the government accountability group American Oversight and former director of Citizens for Responsibility and Ethics in Washington.

That’s exactly the problem with the ‘monuments to me,’” Sloan said, referring to institutions created as legacies to their political namesakes. “We don’t know. The public doesn’t know. But Hatch knows and he’s still in a position to do favors for those who help him because obviously he’d be somewhat indebted to those putting a significant amount of money into this monument to him.”

Questions have already surfaced about Hatch’s legislative priorities with the ties to the Hatch Foundation.

David Baumann, a correspondent for the Credit Union Times, noted in February that Hatch, who has been a supporter of the tax-exempt status for credit unions, recently signaled he wants to look into whether the organizations should pay some taxes to the government as long argued by banks.

Baumann said the fact that Zions Bank President Scott Anderson is also president and board chairman of the Hatch Foundation, could play into why Hatch is having second thoughts on the issue. The Hatch Foundation’s address is listed as Zions Bank’s headquarters.

“Again, there’s nothing illegal here,” Baumann wrote. “All indications are that everyone is following the letter of the law. But if you’re wondering why Sen. Hatch is mouthing the words of many of the nation’s banks, this might be part of the answer.”

Anderson did not respond to a request for comment Friday.

The Hatch Foundation also didn’t respond to a question of how much money it has currently raised — the latest tax filing is from last fall — nor whether it would disclose its donors.

In a statement, the foundation’s director Trent Christensen said the nonprofit “has taken appropriate steps to ensure that its activities comply with all applicable ethics requirements.”

The foundation’s attorney previously said that Hatch would have a limited role in fundraising for the center and that the effort had been vetted by the Senate Ethics Office.

But Hatch’s political arm and the foundation have worked in sync.

Last August, Hatch’s re-election campaign held its annual two day “Fly Fishing & Outdoor Adventure Weekend” at the Montage Deer Valley Resort in Park City, with donors asked to pony up as much as $5,000 to attend.

The following two days, at the same resort, the foundation held the “First Annual Golf Tournament & Outdoor Adventure Weekend” with donors giving $100,000 or more to earn membership in the honorary “Kings Peak Club.”

The foundation and Hatch’s campaign both employ the Larrison Group, a professional fundraiser.

Hatch’s Senate office did not respond to questions about disclosing donors or potential conflicts of interest.

The Utah Republican isn’t the first sitting member of Congress to establish such self-honoring libraries or centers. Senate Majority Leader Mitch McConnell has a center at the University of Louisville and then-Senate Minority Leader Harry Reid set one up at the University of Nevada, Las Vegas.

Hatch’s center, supporters say, is modeled on the Edward M. Kennedy Institute for the United States Senate, which is both a museum to the late senator and nonprofit educational center. That institute reportedly raised $150 million for construction and operations. The Boston Globe reported some $38.3 million in federal earmarks to help fund the institute.

No federal funds have been tapped for the proposed Hatch Center.

Donations to the center that are public include: $125,000 from Altria, which is one of the world’s leading tobacco manufacturers; $65,000 from the Pharmaceutical Research and Manufacturers of America (PhRMA), the lobbying group of the drug industry; and $50,000 from the Biotechnology Innovation Organization, the largest trade group for the biotechnology industry.

Those are just some of the companies that filed reports of their contributions with the Senate. One of those — Merck & Co., Inc., which gave the foundation $20,000 — only did so after the Center for Public Integrity found more than 20 companies and trade groups that had failed to disclose payments to nonprofits aligned with politicians or to honor lawmakers.

Merck originally didn’t disclose the payment to the Hatch Foundation, nor a $5,000 gift to a scholarship fund named for Rep. Jim Clyburn, D-S.C., the Center for Public Integrity found. A company spokesman told the center it amended the reports.

The federal law covering contributions by companies or trade groups to nonprofits aligned with politicians has almost nonexistent enforcement, the Center for Public Integrity noted.

That’s a big loophole, says Sloan of American Oversight, because those groups could give essentially unlimited money to a nonprofit honoring a member of Congress, and may feel pressure to do so if they have business before the House or Senate.

That’s typically the problem: how does somebody say no?” Sloan says.

Hatch plans to retire at the end of this term, ending four decades in the Senate. And while his foundation can continue to solicit donations, companies and trade groups are more likely to give while a politician is still in office and holds power over legislation.

Former House Majority Leader Tom DeLay learned that after leaving office.

A children’s charity set up in his name saw hundreds of thousands of dollars in donations from America’s largest companies and their executives while he was in office. When he left Congress, the contributions dried up, Sloan says.

Hatch does have another pot of money he can draw from for his foundation if he chooses.

The senator has nearly $5 million remaining in his campaign account, and he was fundraising only months before he announced he wouldn’t seek another term.

Federal election law allows campaign funds to be transferred to a nonprofit organization, like the Hatch Foundation. Hatch’s campaign referred questions about that to Hatch’s Senate spokesman, who did not respond to a request for comment.