WASHINGTON — Former Nebraska Sen. Chuck Hagel is a contrarian Republican moderate and decorated Vietnam combat veteran who is likely to support a more rapid withdrawal of U.S. troops from Afghanistan.

As President Obama’s top candidate for defense secretary, Hagel has another credential important to the president: a personal relationship with Obama, forged when they were in the Senate and strengthened during overseas trips they took together.

Hagel, 66, emerged last week as the front-runner for the Pentagon’s top job, four years after leaving behind a Senate career in which he carved out a reputation as an independent thinker and blunt speaker.