TRADE NEGOTIATORS dance to mood music, and the mood music is decidedly sour. Start with the fact that the constituency that favors free trade is fractured and politically ineffective relative to the constituency seeking protection from international competition. The apparel manufacturer and his work force know that competition from China is hurting them, and can hire lobbyists to carry their tale of woe to Congress; the Wal-Mart customer who buys low-priced T-shirts and jeans is unlikely to write his congressman demanding that barriers to trade be kept at a minimum.

That puts a burden on leaders who know that the freeing up of trade in the 60 years since the end of World War II has contributed to increased material well-being for nations that are active in the global economy. They have to represent consumers' interests.

Which is why the performance of E.U. trade commissioner Peter Mandelson, twice forced to resign in disgrace from Tony Blair's cabinet, where he had the reputation of spinner-in-chief, has been so destructive. "Trust," one trade negotiator told me, "is essential to successful trade negotiations." Negotiators have to know that their counterparts speak for the nation or nations they represent, and have to keep their word.

It was because U.S. Trade Representative Bob Zoellick, now number-two at the State Department, and the European Union's Pascal Lamy trusted one another that progress has been made in the past several years in bringing down barriers to trade. Mandelson decided to substitute bluster and spin for trust and negotiation, with consequences

As a member of the USTR advisory committee, I have watched Zoellick maintain his cool and good humor even when provoked by anti-free-trade types, greens who see economic growth as the enemy of the environment, and politicians with very narrow interests to defend. So I find it difficult to believe that he, rather than Mandelson, slammed down the telephone in the midst of their negotiations over aircraft subsidies. And even more difficult to contemplate a Zoellick cowering at the prospect of Mandelson's displeasure.

But I don't find it at all difficult to believe that he reacted negatively when Mandelson first backed away from their agreement to attempt to keep the subsidy battle from developing into a full-blown brawl at the World Trade Organization, and then took to the pages of the Washington Post to carry his arguments over the head of Zoellick to . . . well, to whom? The old spinmaster, already under fire from in Brussels for briefing only selected journalists rather than attending open press conferences, couldn't have expected that a few hundred words from him, blaming the breakdown on Zoellick, would prompt president Bush to fire the man he just promoted, or Congress to call the former USTR on the carpet, or the public to march on Washington to demand Zoellick's head. No. Mandelson was probably following his reflexes: When in trouble, spin, fling a bit of mud, and hope some of it will stick.

SO EVEN IF THE NEGOTIATIONS RESUME, the mood music will remain dissonant. Which simply adds to the threat created by a surprise 67-33 vote in the Senate to slap a 27.5 percent tariff on imports from China.