Carter, 60, is expected to win
Carter previously served as the Pentagon's chief weapons buyer, and as deputy Defense secretary, the No. 2 official. While out of government, he served on advisory boards for both Democratic and Republican administrations.
A native of Philadelphia, Carter holds degrees in physics and medieval history from Yale and a doctorate in theoretical physics from Oxford University, where he was a Rhodes scholar.
Carter first joined the Pentagon in 1981 for a year under President Reagan as a technical analyst. He left to teach at the Massachusetts Institute of Technology before spending nine years as a professor at
In 1993, President Clinton named him assistant secretary of Defense for international security policy, a post in which Carter worked to ensure that the former Soviet nuclear weapons stockpile did not fall into the hands of potential terrorists or rogue states.
Carter was named deputy secretary in 2011 but left again after Obama picked Hagel to succeed