Environmentalists hope the push in Congress for climate change legislation is not overwhelmed by the debate dominating Capitol Hill over changing the U.S. healthcare system. But it might be. Already two months behind schedule and unsure whether enough Democrats will play along, Senate leaders still aim to pass a bill by December when a United Nations summit convenes in Copenhagen to set worldwide goals for reducing carbon dioxide and other pollutants. But as the debate over healthcare legislation rages and with President Barack Obama due to address a joint session of Congress on Wednesday to try to rescue the faltering...