WASHINGTON (Reuters) - The White House offered support on Wednesday for Vice President Dick Cheney, a powerful proponent of the Iraq war, after the conviction of his top aide dealt a fresh blow to Cheney's political reputation and raised new questions about his influence. The trial of Lewis "Scooter" Libby showed Cheney, often portrayed by critics as the shadowy Darth Vader behind the war in Iraq, was deeply involved in an effort to discredit a critic of the administration's prewar intelligence. Libby's conviction on perjury and obstruction of justice charges placed Cheney squarely in the center of a new political...