Remember who the last Secretary of Defense was under a Democratic President? It was a Republican:
On December 5, 1996, President Clinton announced his selection of Cohen as secretary of defense. Cohen, a Republican about to retire from the United States Senate, was the "right person," Clinton said, to build on the achievements of William Perry, "to secure the bipartisan support America's armed forces must have and clearly deserve." In responding to his nomination, Cohen said that during his congressional career he had supported a nonpartisan national security policy and commended the president for appointing a Republican to his cabinet.
Who will be the next Secretary of Defense under a Democratic administration? Seems like a Republican appointee:
Barack Obama and Robert Gates are negotiating policy issues with a view toward Gates remaining Defense secretary, the Financial Times reports, a move that would make the Bush appointee a key member of a bipartisan cabinet that resembles Abraham Lincoln's "team of rivals."
Kind of remarkable that every time Democrats seek elite media and political credibility for having a "bi-partisan" cabinet, they turn to Republicans to manage the Pentagon. Kind of makes you think that Democrats believe Republicans are better at managing both national security, and what is by far the largest department of the federal government. There have been no Democratic Defense Secretaries since 1996, and only eight years of Democratic Defense Secretaries since 1968.