San Jose Mercury News: WASHINGTON — U.S. Sen. Barbara Boxer unveiled ambitious legislation Wednesday to slash the nation’s use of carbon-emitting fossil fuels and reduce the country’s dependence on foreign oil. But the measure, which could emerge as a test of the three-term Democrat’s leadership skills as she girds for a tough reelection fight next year, faces long odds to gain the 60 votes it needs to get through the Senate and on to the president’s desk. Boxer and co-author Sen. John Kerry, D-Mass., …