Last year, Missouri became the latest state to pass a so-called right-to-work law, which prohibits unions from collecting mandatory fees from employees of unionized workplaces. Then-Governor Eric Greitens, a Republican, celebrated by holding multiple signing ceremonies, including one in an abandoned warehouse that he called “a far too familiar sight for many towns across Missouri.” But the party didn’t last long. In fact, the law never had a chance to go into effect. It was suspended after labor organizers and other opponents collected enough signatures to force a voter referendum.

A vote in favor of Proposition A, to be decided on August 7, would make Missouri the 28th state in the country with right-to-work laws, while a vote against would make it the first state to overturn right-to-work by referendum. The outcome has national implications not only for America’s labor movement, which is reeling from years of political and legal defeats (and a concomitant decline in membership), but for the likewise hobbled Democratic Party, which often relies on unions to drive voter turnout.

Proposition A comes on the heels of the U.S. Supreme Court’s decision last month in Janus v. AFSCME, which essentially applied right-to-work standards to public sector unions. Post-Janus, unions in Missouri face a double blow: If Proposition A passes in August, neither private nor public sector unions can collect fees from non-members, even though unions are legally obligated to represent all eligible workers in a unionized shop. That means tighter budgets for organizing and representing workers and for donating to the campaigns of allied politicians, which is a major reason conservative organizations like the National Right to Work Foundation and the Mercer Family Foundation have bankrolled legal challenges to the collection of union fees.

Greitens is no longer the governor of Missouri, having resigned in May amid scandal. But one of his last acts before leaving office was to move up the date for the right-to-work referendum from November to August. Republicans had called for the date change, on the basis that voter turnout would be lower in August—and thus Proposition A stands a better chance at passing thanks to motivated Republican voters. But despite this and the state’s conservative politics, there’s some evidence that unions can win their campaign. An April poll indicated a dead heat, but a July 10 poll published by The Missouri Times showed a sizable lead for the No campaign, which has outraised and outspent its opponents thanks to a significant investment by the International Brotherhood of Teamsters and other unions.

“Once we knew it was going to pass the legislature, we were all very committed to trying to get this on the ballot and have the people of Missouri decide whether or not they believe that this was right for them,” said Derrick Osobase, a political and legislative director at the Communications Workers of America, which has been working closely with unions like the AFL-CIO and community groups like Jobs for Justice. “We really took things back to the basics of organizing, to move not only our members but to go big, and get swathes of the population to understand just how badly right-to-work would affect union workers as well as workers who are non-union.”