Politico: Climate bill supporters are leaning toward exempting big oil companies from a broader cap on greenhouse gases as a way of winning critical support from industry players and key lawmakers. The three co-authors of the Senate climate bill hope the proposal — backed by several large oil companies — will bring a new set of players to the negotiating table. They are floating the idea of levying a carbon tax on each gallon of gasoline, which would be passed along to consumers at the …