On his monthly appearance on KOA radio Tuesday, the Democrat said his biggest mistake was not working closer with the business community on a contentious bill which would have made it easier for unions to organize.
The Democratic Legislature passed it during his first year in office but Ritter, a former union member, vetoed it.
Businesses said it would hurt jobs. Labor unions branded him a traitor.
Ritter said one of his biggest successes was winning an increase in vehicle registration fees to pay for transportation. He says deteriorating roads in Colorado pose a safety issue.