President Clinton picked the perfect backdrop for his first event at this week's World Trade Organization meeting: the Port of Seattle, where acres of cargo containers testify to the billions of dollars in exports that leave this city annually.

But that's hardly the picture most Americans will remember. Billowing clouds of tear gas and rampaging protesters are the images now indelibly linked to the WTO gathering, raising the question of whether Clinton's mission here backfired politically by focusing more attention on the criticisms of free trade than on the benefits he came here to tout.

Several analysts say Clinton had no choice but to come, and they generally credit him with making as strong a case as possible for lowering barriers to trade, considering that riot police had to arrest hundreds--and to fire tear gas at thousands more--just to let him move about the city. They noted, however, that Clinton continually walked a thin line in his 33-hour stay here, trying to juggle competing demands that inevitably made his message hazy at times.

Every time he extolled the virtues of tariff-free borders, he had to reassure two key Democratic constituencies--labor unions and environmentalists--that he wasn't selling them out to appease nations that pollute the land and abuse workers.

"He has to thread the needle," said Brookings Institution presidential scholar Stephen Hess. By defending WTO critics within those constituencies, he said, Clinton inevitably sent a mixed message about the WTO, which may give ammunition to those who oppose his trade policies.

"The problem for him, of course, is his next big fight is going to be in the House of Representatives, defending China's entry into an organization he attacked yesterday," Hess said.

Clinton did not actually attack the WTO, but he expressed sympathy for the nonviolent protesters who did. Congress must vote on closer trade relations with China that WTO membership would imply, and Hess noted: "These pictures [of protesters] have overwhelmed the realities of the scene." That will only serve to muddy Clinton's message on why he feels the trade group and China's entry are so important, he said.

A good illustration of the trade issue's contentiousness for Democrats was the absence in Seattle of the party's presidential candidates, Vice President Gore and former senator Bill Bradley (N.J.). Democratic contenders ordinarily would flock to a city teeming with environmental and labor activists, but both men realized that the WTO meeting would be a no-win tempest. "We've learned that tear gas makes a poor background for a campaign event," said Democratic consultant Mark Mellman.

Andrew Kohut, director of the Pew Research Center, said Bradley and Gore "smelled contention, a contention that is very relevant to the principal Democratic constituencies" of labor and environmentalists. The two candidates can address these groups "in a more dispassioned" setting, Kohut said.

As for the general public, he said, trade is unlikely to be a cutting issue in the 2000 elections because voters are divided and ambivalent on the subject. Most high-income Americans support free trade, Kohut said, while middle-income people have mixed views, and most lower-income Americans tend to fear it.

If the public has a murky assessment of trade, perhaps it helps explain the assortment of protesters who jammed Seattle's streets, including the "Raging Grannies," a "Free Tibet" contingency and scores of others. The demonstrations had virtually nothing to do with race and ethnicity, which have fueled most major U.S. urban disruptions in recent decades.

Instead, WTO protesters argued that unfettered trade encourages countries and corporations to mistreat workers and the environment in a race for profits. In this milieu, Clinton today made one of his strongest concessions to organized labor, signing an international treaty designed to curb child labor abuses. Many poor nations have not ratified the treaty, wary of restrictions in cities and villages where families are desperate to escape poverty, even if it means putting children to work.