I'ts not Rumsfeld's job to resign, it's Bush's to fire him

That seems to be where Fred Kaplan is going.

On Dec. 15, 1993, not quite a year into President Bill Clinton's first term, his secretary of defense, Les Aspin, announced that he would resign. Two months earlier, 18 U.S. Rangers had died, some of them brutally, in the disastrous "Black Hawk Down" raid on Mogadishu. A month before that, the Rangers' commander in Somalia had asked the Pentagon for armored vehicles. Aspin rejected the request. In the raid's aftermath, many blamed Aspin's denial for the Americans' deaths.

Some controversy remains over whether Aspin—who died a year and a half later from heart problems at age 56—deserved to be the fall guy; but it's an irrelevant debate. The key point is that Aspin lost the president's confidence. Once that happens, for whatever reason, the Cabinet officer in question needs to be replaced.