At a recent campaign event at Cornell College, Hillary Clinton told students that she wished super PACs would be banned, but then quickly added in the next breath that “I and others have said we’re not going to unilaterally disarm.”

If Clinton or other candidates really wanted to get super PACs out of this election, there is a simple tool they could use to do it: a bilateral pledge between opposing candidates to eliminate super PAC spending.

This kind of pledge has worked before, and it could work again. In the Massachusetts 2012 Senate race, Elizabeth Warren and Scott Brown proved that when candidates are serious about curbing the influence of super PACs on their race, they can work together to make it happen.

In an agreement known as the People’s Pledge, Warren and Brown made a mutual promise to reject the support of super PACs. They pledged that if a super PAC spent money to support either of their campaigns, whoever benefited from the expenditure would offset it by forfeiting money from their own campaign coffers. The idea was new, bold, and bilateral, and it changed the calculus of spending in the race.

But even beyond the tangible impact that the pledge had on the Massachusetts election, it showed that when it comes to the issue of campaign spending, candidates’ hands are not tied. For any candidate who really wants to do something about super PACs, taking a bilateral pledge such as the one that Warren and Brown pioneered is a real, actionable option.

It’s time for any candidate who says they want to do something about super PAC spending to put their money where their mouth is. A bilateral “no outside spending” pledge is a powerful tool available to all candidates that has the potential to stem the flood of super PAC money – all it requires are candidates who are willing to do the right thing.

In this dark moment in the history of American democracy, what we need are real leaders who will fight to ensure that our elections are about the voices of everyday voters, not just wealthy donors. Who will stand up?