The U.S. Senate passed energy legislation late Thursday night that mandates a 40 percent increase in fuel economy standards by 2020 and calls for a massive expansion of renewable fuels production. But the final bill is far less ambitious than Democrats had originally hoped for, as Republicans successfully derailed a plan that would have funded $32 billion in renewable energy tax breaks by increasing taxes on oil companies and blocked a measure requiring utilities generate more electricity from renewable sources.

The vote, 65-27, came after more than a week of intense debate that demonstrated deep partisan and regional divides over the nation's energy future, as well as the pervasive lobbying power of electric utilities, auto manufacturers and the oil industry.