Unions are outspending opponents in a bid to defeat a right-to-work law in Missouri ahead of a referendum that will serve as a barometer of popular support for organized labor.
A union-backed group in the state has spent $15.2 million ahead of Tuesday’s vote to undo the law passed by the Republican-led legislature in 2017, according to the latest filings with the Missouri Ethics Commission. That is nearly five times the $3.2 million spent by two groups that support the law, which allows private-sector workers to opt out of...