The top lawmakers on the Senate’s defense panel on Friday recommended that a special committee searching for ways to slash the deficit consider some of President Barack Obama’s proposed changes to health and retirement benefits for the military. In separate letters to the bipartisan panel, Sen. Carl Levin, D-Mich., chairman of the Armed Services Committee, and Sen. John McCain, R-Ariz., signaled they were open to cost-saving steps in military benefits, recommendations that have already attracted fierce opposition from powerful groups of retired officers and veterans resistant to change.