Union membership, as a share of workers, fell in all but one state from 1985 to 2010. (Source: Census data.)

In just two and a half years, support for organized labor in California has flipped.

In March 2011, registered California voters had a generally positive view of unions. Some 46 percent said they do “more good than harm” compared to 35 percent saying the opposite, according to a survey conducted by Field Research. Nearly the same share that had a bright view on unions — 45 percent — now say they do “more harm than good,” while 40 percent still have a positive view.

“California voter views of labor unions have taken a decidedly negative turn over the past two and one-half years,” Field’s Mark DiCamillo and Mervin Field said in a statement. They interviewed more than 1,000 registered voters from mid-November to early December. The public is similarly split when it comes to public employee unions, the poll found.

Unions still enjoy support among majorities of Democrats, liberals, voters in union-affiliated households, Latinos, African Americans and voters under 30. Organized labor is considered to do more harm than good by Republicans, conservatives, men, white non-Hispanics, and voters ages 50 to 64, Southern Californians (outside of Los Angeles County) and voters in non-union households. But among all the groups, positivity toward organized labor has eroded.

The shift in the Golden State, mirrors a nationwide trend. Labor union approval bottomed out at 48 percent in the summer of 2009, according to Gallup, and has only recovered slightly since. As of August, approval stands at 54 percent.

Union membership nationwide fell to 11.3 percent of all workers in 2012 from 11.8 percent the year before, according to Labor Department statistics. Only one state saw an increase in the share of workers who were union members between 1985 and 2010, according to Census data. That state was South Carolina, where membership rose to 4.6 percent from 4.5 percent — a share so low it ranks among the bottom five in the nation.