Hours before the state deadline, the unions agreed to pull four so-called "poison pill" measures from the November ballot that took square aim at business interests.
In exchange, business leaders agreed to raise about $3 million to help defeat a right-to-work measure, which would have prohibited union membership or paying dues as a requirement for employment.
"I can't possibly express how relieved we all should be," said Denver Mayor John Hickenlooper. "We can get back to solving problems."
The union proposals would have raised health care premiums for businesses, made corporate executives criminally liable for wrongdoing, limited employers' ability to fire workers, and required businesses to expand their health care coverage for employees.
Political and business leaders roundly denounced the measures. Gov. Bill Ritter Jr., a Democrat, said the proposals would prove devastating to the state's ability to attract and retain businesses.
Labor leaders said they would kill the measures in exchange for the removal of Amendment 47, the right-to-work initiative that earned a spot on the ballot earlier this year. But Amendment 47's sponsor, Jonathan Coors of the Coors beer-brewing family, refused to negotiate.