He was an early and ardent backer of the presidential campaign of Sen. Hillary Rodham Clinton (D-N.Y.) and served on former President Bill Clinton’s National Security Council in the mid-1990s.

Sestak has since backed Obama’s campaign, although he admits he’s not among Obama’s core group of national security advisers.

Still, several Democratic lawmakers have suggested Sestak’s views carry weight among House Democrats. “When he speaks, he has the ear of everyone on the committee,” said Rep. Ellen Tauscher (Calif.), a senior Democrat on the Armed Services Committee. Rep. Jim Cooper (D-Tenn.), also a member of the committee, said Sestak has already emerged as as leader on military strategy. “He’s got the expertise. Democrats should welcome his experience.”

Sestak said, “My belief is that those that have more recent experience and time in the military can help explain why certain [defense] polices” are needed, he said.