As the political odds turn against Proposition 30, Gov. Jerry Brown's tax measure, political insiders are turning their attention, however reluctantly, to the fallout should, indeed, voters reject the sales and income tax hike on Tuesday.

The measure would deliver $6 billion a year in new revenues and should it fail, Brown and the Legislature have already passed $6 billion in so-called "trigger cuts" that would be imposed, overwhelmingly on K-12 schools.

So that would seem to be that. But it's not.

As Brown campaigns – with increasing desperation – for the measure, he insists that were it to fail, he'd refuse to sign legislation changing the trigger cuts to schools. But he has to say that, because the threat to schools is the core of his pitch to voters.

Whether he really would stand pat on the triggers is, therefore, problematic. Brown has never let a seemingly solid public position preclude changing his mind when political winds shift.

What we do know is that his allies in the educational establishment, especially unions such as the California Teachers Association, have no intention of meekly accepting the trigger cuts, even if most school districts have already built that worst-case scenario into their current budgets.

They would not only press Brown and the Legislature to reduce or eliminate the trigger cuts, but most likely would challenge their constitutionality in the courts, because the stakes are not just the 2012-13 fiscal and school years, but the shape of school finance for years to come.

Were the courts to void the triggers, they would take Brown and the Legislature off the political hook of having imposed them – much as the U.S. Supreme Court solved their political dilemma about overcrowding of prisons. "The judge made me do it" sounds much better to voters than "I changed my mind."

The what-to-do-if-Proposition-30-fails quandary is heightened, too, by the simple arithmetic fact that if it does go down in flames, the fiscal problem is much larger than $6 billion.

The 2012-13 state budget actually counts on $8.5 billion from the measure, since the income tax portion would be retroactive to Jan. 1 of this year, and other state revenues are falling below expectations.

Through the first three months of the fiscal year, revenues were running nearly $400 million under budget.

The Facebook stock offering was supposed to generate $1.5 billion in income taxes on capital gains but it's not happening, at least not yet.

The real problem, should Proposition 30 fail, is thus something north of $10 billion and perhaps as much as $12 billion. So even were the triggers to be pulled, Brown and the Legislature would still have a king-size fiscal headache.

This is shaping up as a monumental political rumble.

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