LANSING, Mich.—The first of two laws that would weaken unio power in the labour stronghold of Michigan awaited the expected signature of the governor after it passed the Republican-dominated House of Representatives, while hundreds of protesters rallied at the Capitol.

The so-called right-to-work law dealing with public-sector workers passed 58-51 as protesters shouted shame on you from the gallery and huge crowds of unio backers massed in the state capitol halls and on the grounds.

Foes of the law, including President Barack Obama, are trying to keep the spotlight on this latest battleground in the war over unio rights.

Democrats immediately sought to have the vote reconsidered but failed in that effort.

Still to come was a vote on a second bill focusing on private sector workers.

The Senate approved both laws in early December, and if enacted, Gov. Rick Snyder says he will sign them into law as early as Dec. 12.

If the bills are enacted, it will mark another defeat for the labour movement in the heart of the industrial Great Lakes region, known as the Rust Belt for its once-booming manufacturing sector.

Michigan, a cradle of organized labour, will become the 24th right-to-work state, banning requirements that non-unio employees pay unios for negotiating contracts and other services.

Even with the outcome considered a foregone conclusion, the heated battle showed no sign of cooling as lawmakers prepared to cast final votes.

Hundreds of protesters flooded the state capitol hours before the House and Senate convened, chanting and whistling in the chilly darkness.

Others joined a three-block march to the building, some wearing coveralls and hard hats.

Sen. John Proos, a Republican who voted for the right-to-work bills, said opponents had a right to voice their anger but predicted it would fade as the shift in policy brings more jobs to Michigan.

Democratic lawmakers and unio backers conceded they had little chance of stopping the tide, with Republicans dominating the Legislature and Gov. Snyder pledging to sign the measures into law.

Snyder said the intention is to give workers a choice, not to target unios.

This is about being pro-worker, Snyder said.

In other states, similar battles were drawn-out affairs lasting weeks.

But Snyder, a business executive-turned-governor, and the Republican-dominated Legislature used their political muscle to rapidly introduce and force legislation through the House and Senate in a single day last week.

Demonstrators and Democrats howled in protest, but to no avail.

When asked about the speed at which the legislation moved forward, Snyder said the issue wasnt rushed and that the question of whether to make Michigan a right-to-work state has long been discussed.

For all the shouting, the actual benefit or harm of such laws is not clear.

Each camp has pointed to studies bolstering their claims, but one labour expert said the conclusions are inconclusive.

Very little is actually known about the impact of right-to-work laws, Gary Chaison, a professor of labour relations at Clark University in Massachusetts, said. Theres a lot of assumptions that they create or destroy jobs, but the correlation is not definite.

Democrats contend Republicans, who lost five House seats in the November election, wanted to act before a new legislature takes office next month.

In passionate floor speeches last week, they accused the majority of ignoring the message from voters and bowing to right-wing interest groups.

Obama highlighted the issue during his visit to an engine plant in Michigan.

These so-called right-to-work laws, they dont have anything to do with economics, they have everything to do with politics, Obama told cheering workers. What theyre really talking about is giving you the right to work for less money.

Democratic Sen. Carl Levin and members of the states U.S. House delegation met with Snyder in Detroit and urged him to veto the legislation or amend it to allow a statewide referendum.

Levin said the governor pledged to seriously consider the requests.

In Lansing, leaders of the Democratic minority in the state House acknowledged there was little they could do to stop the fast-moving legislation in the waning days of the session.

However, they vowed to vote against other legislation as a form of protest.