Updated: 9:44 p.m.

Labor leaders scored a victory in Ohio today with the defeat of a GOP-authored state law that had weakened collective bargaining rights for public employees.

Labor unions and their allies had poured millions of dollars into a grass-roots and advertising campaign for a ballot initiative to overturn the months-old law, which imposed collective bargaining restrictions on about 350,000 public workers.

Union officials hailed the outcome as a warning to Republicans considering collective bargaining legislation. “For every candidate who thinks the people who tend to the sick, protect our communities, teach our children and run into burning buildings will be easy targets, think again,” SEIU President Mary Kay Henry said.

The Associated Press called the race, listed on the ballot as Issue 2, at 9:16 p.m.

The law’s defeat was regarded as something of a rebuke to GOP Gov. John Kasich, who had championed the measure, and as a signal that the embattled labor movement remains a force to be reckoned with in 2012. The ballot fight, which pitted leading labor unions against local chambers of commerce and business interests, was closely watched given Ohio’s role as a presidential swing state.

AFL-CIO President Richard Trumka hit the streets to knock on doors and to rally his troops at a Cleveland union hall on the eve of the vote. Total spending by labor groups and their allies, who organized under the banner “We Are Ohio,” totaled $24 million, according to the Associated Press.

Business leaders, who rallied behind the law in a coalition dubbed “Building a Better Ohio,” spent about $8 million.