The Marines Corps is operating without a Senate-confirmed commandant for the first time in more than 160 years after Republican Senator Tommy Tuberville of Alabama again refused to hold a vote on a nominee over his opposition to the Defense Department’s policy to cover the travel costs of employees forced to cross state lines to obtain an abortion. Tuberville has for months held up the promotion and confirmation of hundreds of high-ranking generals and admirals, including members of the Joint Chiefs of Staff.