WASHINGTON — Democratic Sen. John Kerry, who unsuccessfully sought the presidency in 2004 and has pined for the job of top diplomat, vaulted to the head of President Barack Obama's short list of secretary of state candidates after U.N. Ambassador Susan Rice suddenly withdrew from consideration to avoid a contentious confirmation fight with emboldened Republicans.

The exit of Rice and elevation of Kerry shook up Washington on Thursday and was coupled with the potential for even bolder second-term changes in Obama's national security team next month. Chuck Hagel, a former Republican senator from Nebraska, emerged as the front-runner to serve as defense secretary.

The possible selection of Kerry and Hagel would put two decorated Vietnam War veterans — one Navy, the other Army — at State and the Pentagon.