On August 7, the voters of Missouri rejected Proposition A, a ballot measure that would have implemented right-to-work legislation signed by Governor Eric Greitens last year.

Over the past handful of years, the right-to-work movement has scored a number of victories, particularly in the Midwest. Indiana (2012), Michigan (2012), Wisconsin (2015), West Virginia (2016), and Kentucky (2017) all passed legislation making it unlawful for employees to be forced to become a union member or pay union dues as a condition of employment with any particular private sector employer.

Significantly, the right-to-work movement has not suffered any recent setbacks—until now. In Tuesday’s vote, nearly two-thirds of Missouri voters rejected implementation of the legislation, delivering right-to-work its first blow after a string of solid victories in the Midwest.

Some see this as a referendum on the right-to-work movement as a whole, and argue that the movement no longer has the level of support it recently has enjoyed. It remains to be seen whether that assessment is accurate, or whether it is simply a small speedbump in a movement with plenty of momentum.