NEW YORK - So, why did he do it? What led Barack Obama to tap his former adversary, Hillary Clinton, to serve as his Secretary of State, the face and voice of his foreign policy, his emissary to the world?

There are plenty of plausible explanations. One can imagine that he is applying that old adage, "Keep your friends close and your enemies closer." In one stroke, Obama gets control of the Clinton political machine: the network, the donors, and the constituency. And he neutralizes the Clintons' famous skill at corrosive sniping and flamboyant stage-hogging - the kind that led Al Gore and Bill Clinton to be on barely speaking terms during the 2000 Presidential campaign. With this appointment, Obama turns the big guns away from himself - and directs them outward. Shrewd tactics.