Money.Prop 23 opponents, like its supporters, are now tapping out-of-state donors to help bankroll their campaign.With the campaign season revving up, even more money is starting to flow into the campaign to defeat Proposition 23.

Prop 23 is the California ballot initiative that would suspend the state’s landmark climate change law. Its opponents had been relying mostly on the largesse of a California coalition of environmental groups and Silicon Valley’s venture capitalists and tech elite to finance their No on 23 campaign. But now the No forces are tapping out-of-state donors.

On Thursday, they got $250,000 from New York investor Nicolas Berggruen. Berggruen is head of Berggruen Holdings, which has made investments in wind energy projects.

Also last week, Nancy Burnett of Lummi Island, Wash., deposited $100,000 in the anti-Prop 23 coffers. Burnett is a daughter of David Packard, co-founder of Silicon Valley tech giant Hewlett-Packard, and a supporter of Democratic candidates.

And this week, David Bonderman, a Texas investor with TPG Capital, donated $7,500.

Closer to home, Warren Hellman, the wealthy San Francisco investor, banjo player, and blue-grass aficionado, wrote a $75,000 check to the No campaign. The campaign’s supporters are fighting to preserve California’s Global Warming Solutions Act, popularly known as Assembly Bill 32. AB 32 requires the state to reduce greenhouse gas emissions to 1990 levels by 2020 and allows the creation of a cap-and-trade market to meet that mandate.

The bulk of the money financing the pro-Prop 23 campaign has come from two Texas-based oil companies, Tesoro and Valero, and other out-of-state fossil fuel interests. The most recent big donation came earlier this month when Valero gave $3 million to the effort.

Both sides expect the campaign spending to peak somewhere north of $100 million by the time Election Day rolls around in November, with huge amounts of cash rolling in when the traditional election season kicks off after Labor Day.

One person watching the Prop 23 battle closely is Lawrence Goldenhersh, chief executive of Enviance, a California firm that sells environmental compliance software and services — including those that track greenhouse gas emissions — to big industrial companies.

“If AB 32 is sustained by the voters of California, you will have the largest plebiscite in the history of the climate change debate cast by voters in the world’s seventh largest economy,” Goldenhersh told me Tuesday. “If AB 32 survives and Jerry Brown gets elected governor I think you’ll have cap-and-trade nationally by 2013.”

Enviance has clients on both sides of the Prop 23 fight — including Valero — and thus is not taking a position on the ballot measure, according to Goldenhersh. Still, he calls the election the “Normandy invasion of climate change.”

“If Prop 23 passes and AB 32 is suspended or killed then I think there will not be a lot of drive and political appetite to take on a piece of grand climate legislation in Congress,” he says. “People will say, ‘if it’s too expensive for California then it’s too expensive for a little state.'”