Opponents of a right-to-work measure packed the Capitol halls as Missouri's Republican leaders pushed to send the measure to Democratic Gov. Jay Nixon in the Legislature's final week.
A Senate committee voted Monday night to advance the measure to the full chamber for debate. If approved there, it would have to return to the House before heading to Nixon, who has said he opposes it.
The measure would prohibit union contracts with businesses in which fees are collected from non-union employees.
Supporters say it would attract more businesses to Missouri and spur economic growth.
Opponents say it's an attack on unions that would lower wages, make training difficult and reduce workplace safety.
Similar measures were approved in Michigan and Indiana in 2012 and in Wisconsin earlier this year.