What do you do as a politician when billionaire plutocrats drop millions of dollars into a super PAC dedicated to ending your career? Democrats will need to answer this question, and fast. As desperation sets in with the Donald Trump campaign, the Republican National Committee is considering cutting its losses and re-directing funds to save the Republican majorities in the House and Senate. And right-wing super PAC helmsmen, from the Koch Brothers to Karl Rove, have been training their eye on Congress for months. This means dozens of Democrats will likely see attack ads and mailers blanketing their districts this October.

One candidate has come up with a plan to deal with this, and it could become a model for how to, at least, raise awareness of the effort by Big Money to effectively buy congressional races. Zephyr Teachout, a progressive populist hoping to take over an open seat in upstate New York currently held by the GOP, has challenged her opponent to a debate. Not the Republican candidate, but his wealthy super PAC donors.

Teachout, one of several congressional candidates endorsed by Bernie Sanders, is locked in a tossup race in New York’s 19th District against former state assemblyman John Faso. Back in May, a pro-Faso group called New York Wins PAC entered the district with a half-million dollars in advertising, all bankrolled by one man: Robert Mercer, co-CEO of the high-speed trading hedge fund Renaissance Technologies. The secretive Mercer has spent $32 million in the last six years trying to get conservatives elected, including $11 million in support of Ted Cruz’s presidential campaign super PAC.

Paul Singer, the billionaire founder of Elliot Management—a vulture fund that mainly gets rich by scooping up the debt of countries in distress at a discount and bullying them into paying full value—also dumped $500,000 into New York Wins PAC, according to federal election filings. Armed with that stash, Faso easily won his primary in June. And every expectation is that Singer and Mercer will continue to deploy funds targeting Teachout in the general election.

To put things in perspective, it took Teachout the first three months of the year to raise $530,000 for her campaign, which Singer and Mercer each accomplished in support of Faso by signing a check. And this was considered an impressive haul for the former law professor and corruption expert, who challenged New York Governor Andrew Cuomo in the Democratic primary in 2014, winning many upstate counties in and around the 19th District. Teachout’s campaign, which does not accept corporate PAC money, claims its average donation is $19.

Instead of decrying the woeful state of money in politics, Teachout decided to go after Faso’s funders directly, in a video posted by her campaign on Monday. “These are people…who are basically just picking and choosing areas and buying people who are going to represent them,” Teachout says in the video. “So this is very serious. Paul Singer, I challenge you to come here, and have a debate with me.” Later in the day, at her campaign headquarters, she issued the same challenge to Robert Mercer, asking them both to “put your mouth where your money is.”

Teachout highlights some possible debate topics for Singer, including trade deals, education, offshoring jobs, and climate change. But the very act of identifying donors as the real power behind the curtain dovetails with the signature issue for Teachout, the author of Corruption in America: From Ben Franklin’s Snuff Box to Citizens United. Her campaign is organized around curtailing the economic and political influence of large corporations, particularly the way they purchase a piece of Washington with campaign contributions. This has turned candidates into mere cutouts for their funders. So why not ignore the candidate and go after the actual opponents, the guys with all the money?

“We can’t let billionaire donors buy off politicians and get away with being faceless names on a filing,” Teachout told me. “People deserve to know who’s trying to take away their right to choose their representatives.”

The Faso campaign called the challenge grandstanding, and tried to change the subject to support for Teachout in the Communist newspaper The Daily Worker, both of which show that they have no answer for her claims. The whole thing makes Faso look like a mouthpiece for ultra-wealthy masters of the universe, and Teachout just about calls the super PAC money a bribe. “When someone writes a $500,000 check they don’t do it out of the goodness of their heart,” she said at her rally Monday. “These are people probably trying to buy power, and voters should know who they are and what they stand for.”

There isn’t much chance of actually getting Singer or Mercer to drive up from New York City to the Hudson Valley and debate Teachout. Indeed, neither of the hedge funders has responded to the challenge. (I contacted Singer Monday; he didn’t respond to me either.)

But Teachout’s point is more to highlight the ease with which corporate cash can distort campaigns at the district level. Outside dollars in a House race stretch much further than in a presidential contest, simply because there’s less money in the field. In small markets, super PACs can overwhelm a candidate’s delicate spending plans. “I’ll bet $500,000 isn’t even a lot of money” to Singer, Teachout says in her video. “It’s everything in a political campaign.”

This isn’t a substitute for actually changing the campaign finance system, as Teachout understands well; her lead proposal is public financing for all elections. “We need to change the way we fund elections AND not let take over so much power in the marketplace that they squeeze out the little guy,” she said. “Transparency isn’t enough.”

But it does neutralize one way super PACs thrive—through secrecy. Attack ads usually stream across local television screens without any context. By calling out the funders directly, Teachout has tainted those forthcoming ads by associating them with corruption. And that’s a lesson other Democrats might want to heed.