Republican presidential candidate Mitt Romney (left) listens in May as Virginia Gov. Bob McDonnell speaks on his behalf in Portsmouth, Va. Mr. McDonnell recently hinted that he is being vetted as a possible running mate on the GOP ticket. Previously, he had denied that he was under consideration for the vice-presidential spot. (Associated Press)

Republican presidential candidate Mitt Romney (left) listens in May as Virginia Gov. Bob McDonnell speaks on his behalf in Portsmouth, Va. Mr. McDonnell recently hinted that he is being vetted as a possible running mate on the GOP ticket. Previously, he had denied that he was under consideration for the vice-presidential spot. (Associated Press)