John Kerry has been here before. Eight years ago he stood before the assembled representatives of the Democratic Party and accepted its presidential nomination.

When the Massachusetts senator takes the stage on Thursday night, he will no longer be touting his qualifications to be elected president of the United States. But he may be trying out for another job.

Secretary of State Hilary Clinton has said that she plans to relinquish her post soon, a potential second term for President Obama notwithstanding. That leaves an opening for Kerry, who has spent much of his time in the Senate cultivating a deep knowledge of foreign policy, and will address Obama's accomplishments abroad during his Thursday night speech. The Massachusetts senator is chairman of the Senate Foreign Affairs committee.

Kerry has offered a preview with a piece in Foreign Policy that lambasts the Bush administration for its reckless adventurism, spiraling spending on foreign wars, and "bellicose attitude" towards other countries. Kerry praises Obama for a "steady and thoughtful" foreign policy and dismisses Mitt Romney's accusations that the president has been indecisive or not aggressive enough towards America's foes.

"Labeling, as the Romney team has done with China and Russia, is fine for talk-show hosts and for partisan political rallies, but it is a waste of time when pursuing real policy issues with real consequences," Kerry writes.

Kerry's convention role of advocating for Obama's foreign policy prowess conjures 2004, when then-nominee Kerry endured attacks on his war record and ultimately lost to President George W. Bush due, in part, to arguments that it would be unwise to elevate a new commander in chief when the United States was mired in Iraq and battling terrorists.

Since that defeat, Kerry has continued to burnish his reputation as one of the party's leading foreign policy minds from his perch atop the Senate Foreign Relations Committee.

"John Kerry has really found his niche," fellow Democratic Sen. Chuck Schumer told POLITICO. "After you lose the presidency, obviously, you take stock. So John Kerry has gotten over that and has become really the foreign policy expert, certainly in the Senate and one of the handful in the Democratic Party."

Kerry reportedly coveted the secretary of State job that ultimately went to Clinton, settling instead for the chairmanship. But with Clinton on her way out and Romney regularly assailing Obama as someone who apologizes for America, Kerry will have a chance on Thursday to make a case for Obama's foreign policy agenda -- and for his own capacity to guide it.