After shutting down a Democratic filibuster, the Missouri Senate voted 21-13 to approve an anti-union measure that would make Missouri a “right-to-work’’ state.

Republican backers were two votes short Tuesday night of the 23 needed to override a guaranteed veto by Gov. Jay Nixon. They also achieved the final vote by using a controversial and rarely used procedure – called “moving the previous question,’’ or PQ – that angered many of the bill’s opponents.

“That’s the end of discussion for 2015,’’ said state Sen. Scott Sifton, D-Affton, who was among the leaders of the 8 ½-hour filibuster.

Four Republicans joined all nine Democrats in opposing the bill, HB 116, which now goes back to the House for another vote, because of Senate changes.

The bill would bar employers and unions from requiring all workers in a bargaining unit to pay dues. Backers say the ban would make Missouri more attractive to business, while opponents say the aim is to drive down wages and curb unions’ political clout.

The House had passed its version in February, but that tally (91-64) was 18 votes short of the 109 needed to override a gubernatorial veto. The next House vote, which must come by Friday’s adjournment, will show how much progress had been made by Speaker John Diehl, R-Town and Country, in amassing additional support.

Maneuver to force vote rarely used

Sifton – a 2016 candidate for attorney general -- asserted that Senate Democrats will now use procedural moves to gum up the Senate’s works for the remaining three days of session. That could kill or delay action on other significant measures, including a generally routine annual bill authorizing the state to accept $3.5 billion in federal money for health-care programs, mainly the existing Medicaid program.

It’s been eight years since the Senate last deployed the PQ in regular session, although the maneuver was used during last year’s veto session to override Nixon’s veto of a bill requiring a 72-hour waiting period for abortions.

But a stunning difference this time was that Republican leaders deployed the PQ, in effect, against fellow Republicans.

The four Republicans opposing “right to work” included Senate President Pro Tem Tom Dempsey, R-St. Charles, who previously had declined to publicly state his position on the issue. He was joined by Sens. Paul Wieland, R-Imperial; Ryan Silvey, R-Kansas City, and Gary Romine, R-Farmington.

All four Republicans represent districts with large pro-union populations. At least two spoke during against the bill during the Democratic-led filibuster.

Senate Minority Leader Joe Keaveny, D-St. Louis, called the Senate’s PQ action “an affront to the long-held traditions of the Missouri Senate.”

The bill’s chief Senate sponsor, Majority Leader Ron Richard, R-Joplin, contended that the procedure was necessary to advance the bill. "This legislation will bring more businesses to the Show-Me State, increase our job numbers and foster a better environment for workers," said Richard, the former mayor of Joplin, Mo.

Backers point to the 25 states that already are “right to work,’’ saying they are seeing more job growth. Opponents point to statistics showing that the average pay in those states has declined.

Political players weigh in

The Senate vote swiftly attracted reaction, pro and con, from political activists, candidates and groups.

Supporters include the Missouri chapter of Americans for Prosperity, a conservative group with ties to the Koch brothers.

"Missouri is one step closer to joining 25 other states across the nation in giving its workers more freedoms,” said state director Patrick Werner. “…It's great to see Missouri join many neighboring states in helping our local workers and employers."

Opponents, meanwhile, also pointed to support from the American Legislative Exchange Council, another conservative group, and vowed to make the Senate vote an issue in next year’s elections.

Labor leaders already are singling out several Republicans who voted for “right to work’’ after previously receiving union support. They include Sen. Kurt Schaefer, R-Columbia, who’s now running for attorney general in 2016, and Sen. Eric Schmitt, R-Glendale, who’s running for state treasurer.

Missouri Secretary of State Jason Kander, a Democrat running for the U.S. Senate, made clear he’s among the opposition. Kander sent out tweets declaring, “The majority party in #moleg listened to a few special interests instead… I don't know why the majority party decided to spend this session attacking working Missourians, but they'll regret it in 2016.”

Sen. Dan Brown, R-Rolla, contended that "right to work,'' and the Senate vote, will help Republicans statewide. He asserted that 80 percent of his southern Missouri district's constituents back "right to work."

State Capitol correspondent Marshall Griffin contributed to this report.