New York congressional candidate Zephyr Teachout is throwing down the gauntlet to right-wing money men who want to buy elections in secret.

Teachout, who won the Democratic primary for New York’s 19th district in June, this week challenged hedge fund billionaires Paul Singer and Robert Mercer to a debate in light of their contributions to a super PAC that supports her Republican opponent, John Faso.

“The voters deserve to hear directly from the billionaires backing John Faso about what they expect to get from him in Congress,” Teachout said. “When someone writes a $500,000 check they don’t do it out of the goodness of their heart. These are people probably trying to buy power, and voters should know who they are and what they stand for.”

“I’m challenging Paul Singer and Robert Mercer to put your mouth where your money is and debate me directly, not through your mouthpiece,” Teachout said.

Mercer, who is the CEO of Renaissance Technologies and known as one of the “wealthiest, most secretive, influential, and reactionary Republicans in the country,” reportedly wields significant influence over Donald Trump’s presidential campaign. In the past six years, he has donated at least $32 million to Republican candidates, Bloomberg reported in January.

Singer’s track record includes leading a group of hedge funds—often referred to as vulture funds—to capitalize on Argentina’s debt crisis by demanding the full value of its defaulted bonds and pushing the judge in charge of the case to impose daily fines of $50,000 against the country and order it to pay some of the firms’ legal fees. He also supports corporate education reform efforts like Common Core and controversial trade deals such as the Trans Pacific Partnership (TPP).