WASHINGTON — After months of unexplained delays, Acting Defense Secretary Patrick Shanahan stepped down Tuesday before his formal nomination ever went to the Senate, citing a “painful” family situation that would hurt his children and reopen “wounds we have worked years to heal.” President Donald Trump announced Shanahan’s departure in a tweet, and said that Army Secretary Mark Esper would be the new acting Pentagon chief. Acting Secretary of Defense Patrick Shanahan, who has done a wonderful job, has decided not to go forward with his confirmation process so that he can devote more time to his family…. — Donald J.