Energy and conservative interests have pumped more than $8 million into the campaign, including $4 million from Texas-based Valero Energy Corp. and $1 million from a Koch Industries subsidiary.
"We don't feel we need to compete dollar for dollar," said Bob Epstein, a member of the finance committee for the campaign to block the initiative. "We will have enough resources to be competitive."
He says the clear up-or-down vote facing California voters is producing a nationwide response. Much of the coalition's funding, Epstein said, is coming from the fast-growing clean-energy sector.
While the California environmental community is hopeful about defeating Proposition 23, as many as three dozen House Democrats who supported the federal climate change bill are at risk of losing their seats.
If Republican candidates who reject "the sound and settled science" of climate change win their races, "the number of card-carrying members of the 'Flat Earth Society' will rise exponentially in the world's greatest deliberative body," the League of Conservation Voters wrote on its Facebook page.
Americans for Prosperity, a conservative advocacy group, boasts hundreds of candidates nationwide who have signed its "No Climate Tax Pledge" to "oppose legislation relating to climate change that includes a net increase in government revenue." The organization has announced plans to spend $45 million this year on a range of issues.
In contrast, the League of Conservation Voters plans to spend about $4 million. While that's less than the group spent in 2008, league officials say it will be more than 2006.
Erich Pica, president of Friends of the Earth, said that although environmentalists are disappointed over climate change legislation stalling in the Senate this year, "we can't be in such a malaise where we don't understand that our entire agenda over the last five years is going to be completely under attack if these Republican 'tea partyers' get elected."