We're months from when the real fighting starts, but already the labor union and business interests on opposite sides of a November ballot measure are honing their messages.

"The Stop Special Interest Money Now Act" would ban both unions and corporations from contributing directly to candidates. Both could still fund independent expenditure campaigns to support them.

The measure, which hasn't been assigned a proposition number yet, is especially tough on labor because it would ban all payroll-deducted contributions – unions' primary method of raising money for those independent expenditure committees.

Corporations, by contrast, raise the bulk of their political money from shareholders and executives.

Look for labor to attack the measure as faux political reform that kneecaps unions – and, by extension, the working class – and leaves the power of "the 1 percent" virtually unchallenged.

Teamsters Joint Council 42 President Randy Cammack put it this way in a letter written earlier this month to former Los Angeles Mayor Richard Riordan: "It was with great disappointment that we learned of your decision to fund a ballot measure aimed at silencing the voice of working men and women."

Riordan donated $50,000 to Californians Against Special Interests, which then contributed $200,000 to the ballot campaign. He was one of many Republicans who supported a similar measure that failed in 2005.

That year, the unions unleashed a $45 million carpet bombing on Proposition 75 against about $8 million spent by supporters, including a committee set up by then-Gov. Arnold Schwarzenegger. It lost with 53.5 percent of the electorate voting thumbs down, a margin of nearly a half-million votes.

The 2005 defeat mirrored a loss suffered seven years earlier by a similar proposition that would have applied to private- and public-sector unions.

Riordan said in a telephone interview Wednesday that in his view, Stop Special Interest Money Now organizers learned from those first two failures and crafted a measure that can close the deal with voters this time.

The added ingredient: The restrictions on business.

"The opponents try to hide the fact that the initiative restricts corporations. It's not veneer," he said.

But Riordan then acknowledged the politics: "It was put in there to show an equal balance (of restrictions), so that we could get more votes. That's the strategy."

It's still too early to tell whether the strategy will work. The campaigns won't kick into full gear until after the June primary elections.

Meanwhile, the unions are starting to pull away in the money race.

As of Wednesday, the labor-backed campaign to defeat the proposal had collected $5.1 million. The measure's supporters had donated $2.9 million.

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