LANSING, Mich. » The Michigan House approved the first of two right-to-work bills today that would weaken union power in the historical labor stronghold as hundreds of protesters rallied at the Capitol.

The Republican-dominated chamber passed a measure dealing with public-sector workers 58-51 as protesters shouted "shame on you" from the gallery and huge crowds of union backers massed in the state Capitol halls and on the grounds.

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 last week. If enacted, Gov. Rick Snyder says he will sign them into law as early as Wednesday.

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.

"I’m inspired," said Lindsey Curtis, 61, a retired city worker from Flint. "I thought the unions had just rolled over."

Valerie Constance, a Wayne County Community College District developmental reading instructor and member or the American Federation of Teachers, sat on the Capitol steps with a sign shaped like a tombstone. It read: "Here lies democracy."

"I do think this is a very sad day in Michigan history," said Constance, 57.

Sue Brown, a 50-year-old pipefitter from Midland, and her 26-year-old daughter Tracy Brown, a chemical plant worker in Hemlock, held handwritten signs disparaging Gov. Rick Snyder, who last week announced support for the measures.

"It’s disgraceful," said Sue Brown, who said she’s not a union member but fears right-to-work laws would lower wages for all. "The unions and the UAW have created the middle class."

If the bills are enacted, Michigan will become the 24th right-to-work state, banning requirements that nonunion employees pay unions for negotiating contracts and other services.

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

"As they say in sports, the atmosphere in the locker room gets a lot better when the team’s winning," he said.

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

In an interview with WWJ-AM, Snyder said he expects the bills to be on his desk later this week. He said the intention is to give workers a choice, not to target unions.

"This is about being pro-worker," Snyder said.

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

"People don’t understand the labor movement," said protester Sharon Mowers, 54, of Lansing, a United Auto Workers member and General Motors employee. "They don’t understand the sacrifices people made to get us to this point."

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 ramrod legislation through the House and Senate in a single day last week. Demonstrators and Democrats howled in protest, but to no avail.

Asked today about the speed at which the legislation moved forward, Snyder said the issue wasn’t rushed and that the question of whether to make Michigan a right-to-work state has long been discussed.

"There has been lots of time for citizens to contact legislators and share their feelings," he said.

A victory in Michigan, a cradle of organized labor, would give the right-to-work movement its strongest foothold yet in the Rust Belt, where the 2010 election and tea party movement produced assertive Republican majorities that have dealt unions one body blow after another.

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 labor expert said the conclusions are inconclusive.

"Very little is actually known about the impact of right-to-work laws," Gary Chaison, a professor of labor relations at Clark University in Massachusetts, said Monday. "There’s 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.

Criticism of the legislation has come from all the way up the Democratic food chain.

"These so-called right-to-work laws, they don’t have anything to do with economics, they have everything to do with politics," Obama told cheering workers Monday during a visit to an engine plant in Redford, Mich. "What they’re really talking about is giving you the right to work for less money."

U.S. Sen. Carl Levin and members of the state’s U.S. House delegation met with Snyder on Monday 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.

Ari Adler, spokesman for Michigan House Speaker Jase Bolger, chided those in Washington for "trying to tell Republicans in Michigan to slow down and not do our job in Lansing while they fail to resolve the nation’s fiscal cliff crisis or even approve a budget."

Associated Press writers Todd Richmond and Corey Williams in Lansing, Mich., and Ben Feller in Redford, Mich., contributed to this story.