A new independent California poll showing a dramatic erosion of public support for unions should alarm labor leaders, especially those representing government workers.

Residents are fed up with paying for generous salary and benefit packages while listening to cries that it's not enough. And they've lost patience with transit workers' extortive strikes and threats of walkouts that seriously affect commuters' daily lives.

In just two years, according to the latest Field Poll, public attitude in this blue state about unions has switched from positive to negative.

The proportion of registered voters saying unions do more good than harm has dropped from 46 percent to 40 percent; while those saying they do more harm than good has increased from 35 percent to 45 percent. (The poll of 1,002 registered voters was conducted Nov. 14-Dec. 5 and has a margin of error of plus or minus 3.2 percentage points.)

Unions play an important societal role, serving as a check to help ensure fair wages and work rules. For us, the issue is not whether they should exist; it's how they conduct themselves.

Some -- not all -- public-employee groups demand greater compensation while often collecting more than counterparts in the private sector or elsewhere in the nation. They demonize those who dare to do the math, to calculate the short- and long-term economic costs of contracts unions negotiate with officials they often help elect to office.

They portray work conditions as if this were the exploitative early 20th century. They insist on work rules that leave little or no flexibility to adjust to rapidly changing opportunities of new technology and the global economy. And at the slightest deviation from the status quo, they file grievances that squelch progress.

The poster child is BART, where union leader shrill behavior has been offensive. During this year's never-ending negotiations, riders and taxpayers have awakened. They look at their own compensation, they look at the poor condition of the transit system, they watch district directors give away even more -- and they put it all together.

In the Bay Area, unions still enjoy a plurality of support, but the disenchantment has grown markedly in two years.

Moreover, a majority of Bay Area residents, 52 percent, say that public transit workers should not be able to strike; while only 41 percent support their right to walk out.

It's time for unions to work cooperatively and responsibly. And it's time for elected leaders to recognize that labor unions are not their only constituents.