By Brendan O'Brien
MADISON, Wis. (Reuters) - The Wisconsin Senate narrowly approved a "right-to-work" bill on Wednesday that would bar private-sector employees who work under union-negotiated contracts from being required to join their unions or pay them dues.
The bill, which would make Wisconsin the 25th U.S. state with a right-to-work law on the books, cleared the Republican-led Senate on a 17-15 vote following hours of debate marked by periodic angry shouts from opponents in the Senate gallery.
Supporters of organized labor chanted "Shame!" as the legislation was passed and sent for further consideration to the state Assembly, where Republicans also hold a majority.
One Republican senator, Jerry Petrowski, broke with his party and joined all 14 Democrats in the chamber in voting against the measure.
Wisconsin Governor Scott Walker, a possible Republican presidential hopeful, is expected to sign the bill if it reaches his desk.
Walker drew accolades from conservatives across the nation in 2011 when he ushered through legislation curtailing the powers of most public-sector unions in Wisconsin amid large protests at the state capitol in Madison.
Supporters of the right-to-work measure contend it could attract more businesses to the Midwestern state.
"I think this is something that is going to have a direct impact on the manufacturing sector in Wisconsin," Senate Republican leader Scott Fitzgerald said after the vote.
Opponents cast the bill as an assault on organized labor and blue-collar workers that would limit union revenues.
"They are evaporating the middle class, and no one in this room seems to care," Senator Dave Hansen, a Democrat, said during the floor debate.
Right-to-work laws state that employees cannot be required to join a union or pay dues as a condition of their employment. Essentially, the law opens up so-called closed shops, which labor supporters say would diminish union cohesion and their bargaining power.
Republican leaders had fast-tracked the bill, introducing it on Monday and holding a Senate committee hearing of more than eight hours on Tuesday, which the chairman cut short by 30 minutes, citing the threat of a disruption by bill opponents.
Senate floor action on Wednesday was marked from the start by interruptions from protesters in the gallery, who were admonished to follow the rules for decorum.
About 3,000 demonstrators opposed to the measure gathered at about midday around the Capitol Building in an echo of rallies in 2011.
"This is about dignity and the working class," said Freeman Monfort, 83, a union member for 60 years.
State Assembly representatives are expected to take up the bill next week.
(Reporting by Brendan O'Brien; Editing by Scott Malone, Lisa Lambert, Andre Grenon, Eric Beech and Kim Coghill)