ROB PORTMAN has a tough job. As United States Trade Representative he does have the rank of ambassador and a staff of over 200 (considered tiny by the standards of Washington’s bloated agencies). That, and the fact that he is siding with the angels by fighting for freer trade, must be a comfort on a cold night after wearying negotiations with developing countries, some of whose grievances he knows to be legitimate, and with his E.U. counterpart, Peter Mandelson, ever-ready to, er, reinterpret the meaning of his most recent concessions.