SACRAMENTO — If it accomplishes nothing else, Proposition 89 has managed to unite some of California’s biggest campaign contributors against it — labor and business groups that often are at odds in Capitol hallways and election trenches.

The Nov. 7 ballot measure, which would authorize public financing and tougher donation limits for state candidates, has drawn opposition from the California Teachers Association, the California State Council of Laborers, the California Chamber of Commerce, the California Restaurant Association and several insurance companies, among others.

Its chief proponent is another major political player, the California Nurses Association. Other supporters include Common Cause, the League of Women Voters, the Sierra Club and Democratic gubernatorial candidate Phil Angelides. Gov. Arnold Schwarzenegger is opposed.

Chuck Idelson, a spokesman for the nurses, says the proposition gives voters an effective way to deal with “out-of-control election spending and the corruption and appearance of corruption that’s engendered through big-money campaign donations.”

Barbara Kerr, the teachers union president, agrees there needs to be a discussion about how to fix campaign financing but says Proposition 89 isn’t the solution.

“It’s too complicated,” she says. “It’s a flawed proposal. We need to talk about something that might really work.”

But she adds, “If I had a good idea of what would be the best system, I assure you we would have talked about it and proposed it.”

The proposition, similar to laws in Arizona, Maine and Connecticut, would authorize public financing for state candidates who agreed to give up most private donations.

To qualify, candidates would have to collect specified amounts of $5 donations and signatures to demonstrate public support and agree to participate in debates.

The $5 donations would go into a fund to provide the public financing. So would fines for election law violations and a two-tenths percentage point increase in the state’s bank and corporation tax that would be imposed by the proposition.

The legislative analyst’s office estimates those sources would raise more than $200 million a year.

Base amounts of public financing that major party candidates would receive would range from $650,000 for an Assembly race to $25 million for a gubernatorial campaign. Minor party candidates and candidates running unopposed would get smaller amounts.

The proposition also would sharply reduce contribution limits for candidates who shunned public financing. Most donors would be able to give no more than $500 per election to a legislative candidate or $1,000 per election to a statewide candidate.

The current, corresponding limits are $3,300 to legislative candidates, $22,300 to gubernatorial candidates and $5,600 per election for other statewide candidates.

Proposition 89 would impose a $15,000 overall limit on the amount any one donor could give to candidates, political parties and independent expenditure committees in a year.

“This is not some newfangled proposal,” Idelson said. “It’s based on systems in place and working extremely well in a number of other states and municipalities.”

But opponents say it would unfairly impact business and limit the free speech of workers represented by unions.

“We represent 340,000 teachers, and teachers definitely need a voice for our students ... ” said Kerr. “I don’t know why anyone would find it offensive that teachers and students want a voice in Sacramento.”

Allan Zaremberg, president of the California Chamber of Commerce, said taxes shouldn’t be raised to pay for political campaigns.

“Using scarce tax dollars on negative campaigns ... is not something the public wants to spend their very dear tax dollars on,” he said.

“The real story here is what this does is create a level playing field,” Idelson said. “That’s what they most oppose, that we would be on equal footing.”

Opponents also complain that the proposition wouldn’t stop wealthy candidates from spending unlimited amounts of their own money on their campaigns. Courts have not allowed caps on those expenditures.

And opponents suggest Proposition 89’s contribution limits are too restrictive to pass court challenges, but Idelson disagrees.

“This is modeled after successful laws that have worked in other states, laws that have met constitutional tests,” he says.

Robert Stern, president of the Center for Governmental Studies, a Los Angeles-based political think tank, says Proposition 89 wouldn’t cure all of the state’s campaign finance problems but would “change California pretty dramatically in terms of who runs and where they get their money.”

“It will allow more people to run who aren’t wealthy and aren’t connected to wealthy special interests,” he said. “I think it will reduce the impact of special interest money but not eliminate it. ... It would be a major improvement but not the Holy Grail.”