Linda Kenney, a professor of microbiology at the University of Illinois at Chicago College of Medicine, says something has to be done about the “dumbing down of science” by politicians. After reading about a group called 314 Action working to elect scientists to public office, it did not take much for Kenney to open her wallet. Now Kenney says she donates about $100 monthly to the group. “This is way overdue,” she says. “I don’t know if it’s money well spent, but it’s something I can do and I believe in it.”

Kenney agreed to discuss her contirbutions for this story. But 314 Action plans to raise $5 million to $7 million for current candidates, and it will be impossible to know where the bulk of the money is coming from. That is because the group, named for the first three digits of pi, is taking advantage of a widely used and controversial campaign finance apparatus: a nonprofit arm that does not disclose its donors.

This practice has been dubbed the use of “dark money” in the political world. It has become fairly standard for groups of all stripes—from Republicans to Democrats and from powerful business interests to unions. Planned Parenthood uses these undisclosed donations. So does the National Rifle Association. It is legal. But the practice also means the general public cannot learn much about the original sources of money behind political candidates.

         Aside from its nonprofit, 314 Action is also raising and spending money via a separate political action committee, or PAC, that is required to report donors to the Federal Election Commission (FEC). But most of the group’s funds will come from the nonprofit arm, which has no such requirement. It is registered as a “social welfare” group under section 501(c)(4) of the U.S. tax code. Nonprofits such as this, which advocate for policy issues, are forbidden from contributing directly to candidates. Nor are they allowed to make electioneering their primary activity. But they are allowed to spend some of their money on political TV ads, radio spots, mailers and digital communication  to support or oppose candidates without having to disclose donors.

Josh Morrow, 314 Action’s executive director, says that for the most part the group uses its nonprofit arm to train candidates and for issue-based advocacy such as an online petition in support of the Paris climate agreement. But in this year’s elections, for the first time, money from the nonprofit will be used to buy political ads that help candidates who are often scientists running their inaugural campaigns. “For us, it’s about leveling the playing field for our nontraditional candidates,” Morrow says. He also notes most donors contribute relatively small amounts, not millions of dollars.

A 2010 landmark U.S. Supreme Court ruling changed the campaign finance landscape by opening the door for corporations, as well as nonprofits like 314 Action, to spend money to influence the outcome of elections with ads. In addition, lax enforcement of campaign finance laws at the gridlocked FEC has allowed the use of anonymous campaign money to surge. According to the Center for Responsive Politics, there has been more than $680 million in dark money spent on federal elections since 2012.

Adav Noti, a former associate general counsel at the FEC, says it would be better if the group backing science candidates as well as other politically active nonprofits disclosed its donors. “But that doesn’t necessarily mean they’re nefarious,” he says. “There are nonprofits who legitimately engage in some electoral activities that are ancillary to their primary goals, and they don’t disclose their donors because it’s not required—and for the most part that’s not particularly problematic,” says Noti, who is currently the director of trial litigation at the Campaign Legal Center, a Washington, D.C.–based organization pushing for more disclosure of money in politics.

So far, 314 Action has raised about $1.4 million through its nonprofit arm, and can use some of that for political ads intended to influence the outcome of elections. The group’s PAC, which discloses all of its donors, has raised about $506,000. It is a so-called hybrid PAC, which allows 314 Action to donate up to $5,000 directly to congressional candidates while also being able to raise and spend unlimited sums for political ads.

Last year 314 Action supported candidates in New Jersey and Virginia, but Morrow says the group’s role was limited to helping raise money. The group has substantially expanded its efforts this cycle, already endorsing about 15 congressional candidates, all Democrats, and several more at the local level. TV ad buys totaling around $2 million have already been reserved in Los Angeles, Detroit and Seattle for the final two weeks leading up to each state’s primaries, according to a report in the publication Roll Call.

Asked if 314 Action would be willing to reveal its nonprofit donors, Morrow says: “I’m open to it. But it’s not something we’ve discussed.” He adds that “the distinction between us and a lot of dark money groups is we are really funded by scientist and STEM advocates. There’s no $5-million anonymous donors.”

Michael Fried, a professor emeritus of mathematics at the University of California, Irvine, says he’s been donating to 314 Action since it started. Fried is listed a donor to the group’s PAC, but he says he recently gave his biggest contribution—$10,000—to the nonprofit for an education program. “I’m not an oil guru. I’m not an asset advisor. I am a well-paid professor,” Fried says. He says he donates to 314 Action because he believes in the group’s mission and “they have gone from nothing to something in a very short time without getting a big head.”