His presidency has been rated as one of the worst in historians' polls, although his favorability ratings have improved since leaving office. He was honorably discharged from the Air Force Reserve on November 21, 1974. On July 25, 2000, Bush surprised some observers when he selected Dick Cheney—a former White House Chief of Staff, U.S. Representative, and Secretary of Defense—to be his running mate. At the time, Cheney was serving as head of Bush's vice presidential search committee. He was honorably discharged from the Air Force Reserve on November 21, 1974. On July 25, 2000, Bush surprised some observers when he selected Dick Cheney—a former White House Chief of Staff, U.S. Representative, and Secretary of Defense—to be his running mate. At the time, Cheney was serving as head of Bush's vice presidential search committee. Soon after at the 2000 Republican National Convention, Bush and Cheney were officially nominated by the Republican Party.