Denver - A labor-union campaign in Colorado to tighten restrictions on layoffs and crack down on corporate fraud could put Democrats in an awkward position as they gather here in August for their presidential convention.

    Unions are pushing to get a total of six measures on the fall ballot, all of them opposed by small-business owners and corporate interests.

    "If they pass, it would be like putting a big 'Do Not Locate Your Business Here' sign on Colorado," said John Brackney, president of the South Metro Denver Chamber of Commerce.

    Big labor groups said they will pump as much as $35 million into Colorado to pass their own measures and defeat a rival initiative promoted by business interests. That puts pressure on Democrats, who get labor backing but are loath to support costly mandates on business during an economic downturn.

    A rally in Denver Tuesday will kick off signature drives to put two of labor's top priorities on the November ballot in the state.

    One measure would make Colorado only the second state in the union, after Montana, to require that employers prove every layoff is for a "just cause." A second measure holds executives personally responsible if they fail to prevent their firms from committing misdeeds, such as polluting a river or cooking the books. Backers said this would be the strongest corporate-fraud law in the nation, subjecting executives to both criminal prosecution and civil lawsuits.

    The coalition backing those ballot measures already has raised nearly $1.6 million, including large contributions from the Service Employees International Union, the Teamsters, the International Brotherhood of Electrical Workers and the National Education Association.

    Meanwhile, another union representing food and commercial workers is pushing four additional ballot measures. They would require all employers to give annual cost-of-living raises, mandate health coverage at any business with more than 20 employees, permit injured workers to sue outside the workers' compensation system, and raise property taxes on businesses.

    Each initiative needs the signatures of 76,000 registered voters by early August to get on the fall ballot. That is a relatively low bar compared with other states.

    Manny Gonzales, of United Food and Commercial Workers International Union, Local 7, said the measures are "strictly focused on protecting Colorado's middle class." But others said they would impose an unprecedented burden on businesses of all sizes. "I think they would turn the lights out in the state," said Ray Hogler, a professor of labor law at Colorado State University.

    Two years ago, Colorado voters approved a labor-supported constitutional amendment to raise the minimum wage. The new crop of measures has similar populist appeal, and Mr. Hogler said he expects voters will warm to them.

    For their part, business interests are pushing a right-to-work initiative, which would let workers in union shops opt out of the union. That measure recently qualified for the November ballot.

    Predicting a bitter and costly fight, top Colorado Democrats spent weeks pleading with both sides to drop their initiatives and stand down from what Gov. Bill Ritter, a Democrat, has described as "mutually assured destruction." Neither side budged.

    Denver Mayor John Hickenlooper, also a Democrat, said he plans to vote "no" on all the measures.

    Candidates on the November ballot may have a harder time staying neutral as Colorado falls under the spotlight. Not only is it hosting the convention, but there is a race for an open U.S. Senate seat, and Democrats plan a push to swing the state from red to blue in the presidential race.

    Some pundits suggest labor's ballot fight could aid Democrats, by energizing their supporters. However, Pat Waak, chairwoman of Colorado's Democratic Party, said she is concerned unions might cut back on donations to candidates because they are devoting so many millions to the ballot fight. "It gets down to how much money they have left," Ms. Waak said.

    Mitch Ackerman, president of the service employees union in Colorado, said he hopes the union can continue backing candidates - so long as those candidates back the union's goals.