Democrats have often feared big money in American politics, perhaps because most of it doesn’t go their way. When the Supreme Co

Democrats have often feared big money in American politics, perhaps because most of it doesn’t go their way. When the Supreme Courts truck down the caps on aggregate campaign donations last week, Republicans, broadly speaking, cheered and Democrats jeered. In the 2012 election cycle, four of the five biggest donors to super PACs — independent groups that raise money, often from the extremely rich, and spend it on outlandish political advertising — were Republicans. Tom Steyer, a San Francisco-based billionaire who worries about climate change, is doing his best to help his fellow Democrats get over their qualms. Perhaps best known for his opposition to the proposed Keystone XL oil pipeline, Mr. Steyer, a former hedge-fund investor, was the biggest super PAC spender last year, dropping $ 11.1 million into his two groups. This year he looks likely to repeat that feat, hinting that he will invest at least $50 million in one of them, the Next Gen Climate Action Committee (NGCA), and that he will be seeking the same amount from other donors. The money will be spent to help elect politicians who share Mr. Steyer’s environmental views, or kick out those who do not. In November’s mid-term elections, all 435 seats in the House of Representatives and 36 in the Senate will be up for grabs. So will 36 governorships and countless state legislative seats. For NGCA to spend on any given race, says Mr. Steyer, three conditions must apply. First, the leading candidates must have differing views on climate change (so Democratic fans of Keystone should be safe; their Republican opponents probably agree with them). Second, "something substantive" must have a chance of happening if the NGCA-backed candidate wins. Third, the race should have the potential to affect the national climate debate. That conversation has been stalled since a Democratic cap-and-trade bill died in the Senate in 2010. Nor is major environmental legislation likely in the next Congress (although Barack Obama is pursuing various emissions-reduction schemes through the Environmental Protection Agency). That is why Mr. Steyer expects state races to occupy "the bulk" of his efforts this year. Rick Scott, the Republican governor of Florida, who has doubted the science of global warming, can expect to feel it, for example. The same may go for Tom Corbett, facing a tight reelection race for governor in Pennsylvania. The team is also looking closely at regional climate-change schemes. Mr. Steyer likes the Regional Greenhouse Gas Initiative, a shared effort between nine states in the north-east to reduce carbon emissions from power stations, and could intervene in elections in states that are considering joining. Out West, last October Mr. Steyer helped broker the Pacific Coast Action Plan on Climate and Energy, a non-binding agreement between three American states and British Columbia in Canada. But sceptical legislatures in Oregon and Washington state have blocked bills that could turn words into action, such as carbon pricing, and so these too are likely to be targets (although a Steyer-backed Democratic candidate for the Washington Senate flopped last November). California, Mr. Steyer’s home state, has proved more willing to press ahead. Its cap-and-trade market, for example, has been operating smoothly for over a year; Quebec joined in January.