(CNN) - Robert Portman, the director of the Office of Management and Budget, formally endorsed John McCain's White House bid Tuesday, hailing the Arizona senator as a "proven leader with a track record of breaking through partisan gridlock in Washington."
"He has been an effective champion for fiscal responsibility and pro-growth economic policies. No one is a more committed advocate for our men and women in uniform, and no one understands better the threats America faces," Portman, a former congressman from Ohio, said in a statement released by the campaign.
Portman is often mentioned as a potential pick for vice president given his fiscally conservative credentials and ties to Ohio - a crucial swing state in the general election.
McCain's campaign also announced the backing Tuesday of six former chairmen of the Republican National Committee.
Related: Potential V.P. picks stay mum
– CNN Ticker Producer Alexander Mooney