If you haven’t yet heard, California’s Proposition 23 has become a lightning rod of debate about the clean energy and air future of not just California, but of the nation. The New York Times yesterday called it a showdown, saying that it has “jolted environmental leaders who are worried that a vote against the law in this state — with its long history of environmental activism — would amount to a powerful setback for emission control efforts in Washington and statehouses across the country.”