* Critics say proposal would be death warrant for state economy
* Few states have made unionizing constitutionally protected
* Vote expected to boost turnout for presidential election (Adds background on Michigan in 12th paragraph)
By James B. Kelleher
DETROIT, July 29 (Reuters) - After suffering a string of political setbacks in the U.S. industrial heartland, organized labor hopes Michigan voters will help turn the tide in a November election by supporting a state constitutional amendment for the right to unionize.
The union-backed ballot proposal would make collective bargaining a constitutionally protected right and cripple efforts to pass so-called "right to work" legislation in the state. Critics say the measure, which would cover private as well as public employees, would be a "death warrant" for Michigan's economy because it would discourage businesses from bringing new jobs to Michigan and encourage some already in the state to leave.
Experts say the union push, which included a door-to-door weekend canvassing effort by delegates attending the Detroit convention of the American Federation of Teachers, is likely to increase voter turnout in the fall presidential election in a state that is too close to call.
A poll released last month by Mitchell Research showed President Barack Obama and Republican presidential candidate Mitt Romney in a dead heat in Michigan, where Obama easily beat Republican John McCain in 2008.
"It's a critical time and a critical issue," said Marva Boatman, an AFT conference delegate who is a special education teacher from Washington, D.C., as she rang doorbells and knocked on doors outside Detroit on Saturday, asking voters to support the amendment.
Only a handful of states, including Florida and Missouri, have made unionizing an activity protected by the state constitution, according to F. Vincent Vernuccio, director of labor policy at The Mackinac Center for Public Policy, a free-market think tank focused on Michigan.
But the Mackinac Center and other critics, including the Michigan Chamber of Commerce, say the amendment - which supporters call the "Protect Our Jobs Act" - would be a more sweeping measure.
They claim it would allow public-sector unions to use contract negotiations to override acts of the legislature, such as laws limiting how much taxpayers pay for government employee healthcare.
"It is extremely radical and would fundamentally change the power structure in Michigan," Vernuccio said.
CALLED "ECONOMIC DEATH WARRANT"
Greg Mourad, vice president of the National Right to Work Committee, said if voters approve the measure they will be "signing their own economic death warrant.
"It would make it significantly harder for Michigan to create and attract jobs," Mourad said.
Michigan has been hard hit by the decades-long struggle of the Detroit-based automakers and the continuing restructuring of the domestic car business. One measure of just how much that restructuring has realigned politics in the state can be seen in the fact that Romney, who has criticized the 2009 auto bailout backed by the once-dominant United Auto Workers union, is running so close with Obama.
Supporters of the "Protect Our Jobs" measure submitted nearly 700,000 signed petitions - twice the number needed - to have the proposal put on the November ballot.
The Michigan Department of State is expected to certify the petitions next month after the deadline passes for opponents to submit challenges to the signatures.
Vernuccio said recent polling had shown voters equally divided over the measure.
According to documents filed last week with the Michigan Secretary of State, organized labor and others have raised more than $8 million to support pro-union initiatives in the state this fall.
In addition to the constitutional amendment, unions also are asking Michigan voters to repeal a law giving state-appointed emergency managers wide powers to cut spending in municipalities and school districts deemed to be experiencing a "financial emergency."
That law has been used to take over more than half a dozen financially ailing cities and school systems in the state in recent years and to void union contracts.
Since the Republican victory in the 2010 midterm elections, organized labor has taken a beating in the Midwest, a region that was once a union stronghold.
In June, a union effort to oust Wisconsin Governor Scott Walker, a Republican who curbed collective bargaining by public employees in his state in 2011, was handily defeated.
Earlier this year, Indiana became the country's 23rd state, and the first in the industrial heartland, to pass "right to work" legislation that bars employers from signing union contracts that require employees to pay fees for representation. (Editing by Barbara Goldberg and Bill Trott)
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