JUDY LINLOS ANGELES (AP) â¿¿ A national effort to cripple organized labor has crossed into California as voters Tuesday consider a ban on the way unions have traditionally raised money for political causes. Following up on recent efforts to dilute the strength of unions in Wisconsin, Ohio, Indiana and elsewhere, business interests and wealthy Republicans have contributed tens of millions of dollars to pass Proposition 32. California's major labor groups have responded with equal force, spending at least $75 million to defeat it. Supporters describe Proposition 32 as a cure-all for special-interest politics by prohibiting corporations and unions from collecting money for state political activities from employees or members through paycheck deductions. But it would hit unions the hardest because corporations do not typically deduct money from employee pay for state political activities and because there are few unionized employees left in the private sector. The initiative would prohibit unions and corporations from making donations directly to state candidates but would not stop corporations, the wealthy or unions from spending unlimited amounts of money on political campaigns through so-called independent expenditure committees. Yet because unions would have a much harder time raising money, the political playing field would be tilted heavily in favor of corporations and rich individuals. Overall, there are about 2.4 million union members in California, and the money collected from them has helped make teachers, prison guards and nurses among the most powerful interest groups in Sacramento. They overwhelmingly support Democrats, who control both chambers of the Legislature and every statewide office. Labor leaders are asking California voter to reject an initiative they say would silence workers. Voters rejected similar ballot questions in 2005 and 1998. The California Teachers Association, the state's largest teachers union, has led the charge against Proposition 32. A number of committees have been formed to support it. More than $4 million has come from the American Future Fund, an Iowa-based organization that supports conservative causes with ties to billionaires Charles and David Koch, who have provided crucial support to the tea party.