If approved, the California proposal would become law in July and would greatly limit labor's role in November's pivotal gubernatorial election.
Democrats have high hopes of retaking the governorship of the nation's largest state.
Polls show that 70 percent of voters support the proposal, and Gov. Pete Wilson, a Republican, today predicted in an interview with Reuters that it would pass easily. But labor officials here today would only cautiously predict they could win the California vote. Similar proposals have been introduced in 30 other states and are actively being pushed by conservatives and business groups. We will not be able to keep up with the other side. They're going to outspend us two to one.