Missouri Republicans have used their large majorities to send a "right-to-work" measure to Democratic Gov. Jay Nixon but appear to lack the support to override an expected veto.
The Missouri House gave final approval Wednesday to a bill that would prohibit workplace contracts that require union fees to be collected from nonmembers.
Supporters say the legislation would attract more businesses to the state and spur economic growth, while opponents assert that it would undermine unions and lead to lower wages.
Senate Republicans used a rare procedural move to cut off debate Tuesday evening and force a vote.
But both the Senate and House votes were short of the two-thirds majority that would be needed for a veto override.
Although Republicans hold supermajorities, some Republicans have joined Democrats opposing the bill.
