The Center for American Progress, the preeminent liberal think tank in Washington, is poised to exert outsized influence over the 2016 president race and — should Hillary Clinton win it — the policies and agenda of the 45th President of the United States. CAP founder John Podesta is set to run Clinton’s presidential campaign, and current CAP president Neera Tanden is a longtime Clinton confidante and adviser. CAP recently rolled out a major blueprint for combat wage stagnation and inequality that many view as a template for a Clinton economic agenda, and there are surely more major policy statements to come.

So interest in CAP’s funding sources — and its internal workings in general — is likely to intensify and take on a political cast.

Today, CAP is revealing its major 2014 donors, after taking some criticism for lack of transparency. The organization provided me two lists of its donors, which you can read right here and right here. The first is for the C (3), the nonpartisan think tank arm; the second is for the more political, issue-advocacy-oriented c (4).

Perhaps most notably, given CAP’s advocacy for an economically progressive agenda, is that CAP’s top donors include Walmart and Citigroup, each of which have given between $100,000 and $499,000. Other donors to CAP — a leading advocate of health care reform — include the Pharmaceutical Research and Manufacturers of America, which represents leading biotech and bio-pharma firms, and Blue Cross Blue Shield Association, both of which have given up to $49,000.

Still, many of CAP’s donations appear to be drawn from conventional funding sources for progressive organizations, including labor unions and charitable foundations.

“We’re proud of our donors,” CAP president Neera Tanden said in an interview. “We’re very diversified. We have a very low percentage of corporate donors. We have a wide panoply of individual and foundation supporters. Given that transparency is a progressive value, we wanted to get our list out there.”

CAP’s approach to transparency has stirred controversy in the past. As the Huffington Post’s Ryan Grim reported back in 2013, the group had “for years faced a tension between its call for campaign finance transparency and its unwillingness to disclose its own donors.” The opacity of funding of many influential groups in Washington, DC, has long been seen as a problem by the left. It gained additional scrutiny when Senator Elizabeth Warren called on banks to disclose their contributions to think tanks, on the theory that such contributions could compromise the quality of the think tanks’ research and analysis, which could have serious consequences, given their influence over policy makers.

After the news broke that CAP founder John Podesta was moving to the White House, the organization released a list of its 2013 donors. Podesta will now run Clinton’s campaign.

Last spring, a non-profit group called Transparify released a report alleging that many non-profit groups — on both sides — that operate through various channels to wield considerable influence over policy-making in Washington have a bad track record in revealing funding sources. Among the groups it singled out was CAP. At the time the New York Times summed up the stakes this way:

The question about the disclosure of donors is not simply an academic one. These institutions often play a major role in shaping public policy, and their reports are widely distributed among lawmakers and are often cited by corporate lobbyists as they push legislation that could benefit their bottom lines. What is often unknown is what role different industries — or even their lobbyists — play in delivering money to the research groups that generate these reports.

Pressed on whether sources of funding could end up coloring the result of research, Tanden replied that the very fact that the group criticizes its own donors shows their money does not influence their research. “We’ve taken support from people, and we’re vocal critics of some of their policy positions,” she said, citing Walmart and defense contractors as examples.

“Our policy proposals and the work we do — whether it’s attacking deregulation of the banks or criticizing defense spending — we take our positions on the merits, and for no other reason,” Tanden said. “CAP is different from many other organizations in that we do not take corporate money for directed research.”

CAP has already exercised considerable influence over the Democratic policy machinery in Washington, and the group’s influence could very well grow, particularly if Clinton is elected president. So more scrutiny of the organization is probably inevitable. But even if it is increasing its own transparency, the broader problem will remain.

“Whether CAP was pressured into it or not, they are continuing the practice of releasing their donors, which will aid scrutiny,” said David Donnelly, the president of Every Voice, which advocates for campaign finance reform. “The bigger point here is that non-profits depend on a wide array of funding sources, and most non-profits choose not to be transparent about them. While it’s more important to know the money trail for elected officials, lobbying firms, and groups that influence elections, it does serve the public interest to know where nonprofits that are influencing the policy-making process get their funding.”

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UPDATE: A number of journalists, such as Dan Berman and Ken Vogel, have rightly pointed out that CAP’s donors include three who gave over $1 million who are labeled “anonymous,” and a number of others who are similarly labeled, and have questioned whether CAP is being fully transparent. My understanding is that these are donors who explicitly asked to remain anonymous.

This raises an important line of inquiry that goes beyond CAP. The right question is: Should non-profits that are striving for transparency reject all donations coming from donors who explicitly request such anonymity?

I asked Transparify, the organization that has gotten this discussion going, to comment on the situation. The group’s officials suggested they are okay with non-profits accepting a small percentage of donations from anonymous donors, provided that percentage remains below 15 percent, on the theory that non-profits have an understandable reason for not turning away this money. They emailed:

Transparify strongly welcomes the Center for American Progress’ recent shift towards greater transparency. While we have not formally assessed and rated CAP’s new disclosure level yet, it is clear that it represents a substantial improvement over CAP’s previous level of disclosure. CAP’s move reflects a broad and significant shift by the American think tank community as a whole towards greater transparency over the past year.

Some commentators have highlighted the fact that CAP, like some other think tanks, has not disclosed the names of some of its donors. Transparify obviously encourages full disclosure, but at the same time realizes that large institutions in particular may need to take one step towards transparency at a time. CAP is definitely moving into the right direction.

Should there be anonymous donors at all? As Transparify has documented, there are various sides to the debate. Some donors do not want to be named. While we prefer as much transparency as possible, our ratings at this point make allowance for up to 15% of donations being anonymous. The rationale is that sensible organizations typically will not risk their reputations for a small portion of their funding. This rule-of-thumb is not meant to settle the discussion on anonymous funding. It is intended to make it possible to have a constructive debate on such funding, in the first place.

Meanwhile, a small (and rapidly shrinking) minority of American think tanks continue to dig their heels in and refuse to open their books. Its understandable and legitimate that the public is focusing on the funding makeup of institutions who are opening their books.  However, in terms of research integrity, what is far more worrying is what is completely unknown — the funding makeup of opaque think tanks.

It’s important to ask who is funding 3% of a more transparent think tank’s operations. But it’s even more important to ask opaque think tanks who do not disclose who their main donors are why they continue to keep their books closed while their peers are progressively disclosing more data.