California has long been a union stronghold, but a new poll suggests voters are gradually taking a more negative view of organized labor.

The independent Field Poll released Friday said that by a narrow margin, more voters said unions do more harm than good, as opposed to those who see labor as beneficial.

The slide in support in the strongly Democratic state represents a flip from a 2011 survey, when more voters said unions resulted in more good than harm.

The poll of 1,002 registered voters says that 45 percent said labor unions do "more harm than good."

Forty percent said unions do "more good than harm."