As a bargaining tool in the politics of climate change, expansion of oil and gas leasing off the US always has raised problems. After the Deepwater Horizon tragedy, even politicians eager to deploy it must be having second thoughts.Senate sponsors of climate-change legislation are desperate to act. The House has passed a bill that would cap emissions of greenhouse gases and create a broad market for emission allowances.But many senators are wary. Democrats, especially, have big political problems after voting for unpopular health-care reform legislation. They want no part in another political brawl months before an election.Many senators, too, recognize that the House bill is political ju...