Many Democrats have a hard time understanding why Republicans want to keep investigating the Sept. 11, 2012, terrorist attack in Benghazi, Libya.Some see the GOP trying to score partisan points for this November's midterms. Others see a plot to undermine Hillary Clinton's 2016 prospects. Republican sources on Capitol Hill say that, in general, the Pentagon's cooperation has been a model of how to deal with such an investigation, while the State Department and White House have been models of what not to do.If the rest of the administration had followed the military's example, the Benghazi controversy would likely be over by now.The probe started with three questions.