Obama takes national stage to defend his energy agenda

President Barack Obama accepts the nomination of his party for a second term Thursday evening with a speech that will seek to show broad contrasts with Republican Mitt Romney, campaign aides said.

Briefing reporters on condition of anonymity, those aides declined to give details in advance of excepts of the speech that were to be made available early in the evening. "The key tonight in the president's view is to lay out the choice for the American people, really bring it into focus for the American people," an aide said.