Why? For most of the present US administration, Bob Zoellick had been the US Trade Representative. Zoellick was an old hand, wise in the ways of both trade and Washington. But when Condelezza Rice was appointed Secretary of State, Zoellick went over to become her deputy. His successor, Rob Portman, was a Congressman from Ohio who had been involved with the nuts and bolts of trade legislation for many years. He was serious and experienced, with friends on Capitol Hill. Now Portman has resigned as Trade Representative to head the Office of Management and Budget; a bigger responsibility, but not connected to trade.
The upshot is that the USTR position will now be empty for some time, the current president’s authority to negotiate agreements that the Congress cannot amend is expiring soon, and the administration sees little hope of progress in the Doha round before it leaves office. Looks like it could be the end of the line for Doha.