Mickey Kantor has a vivid memory of August 1993. The North American Free Trade Agreement was in trouble. Though the agreement had been signed the year before, during the administration of George H.W. Bush, the newly elected Bill Clinton had promised to attach side deals to the pact to guarantee minimum labor and environmental standards.

The Mexican government hated them — they were thinly disguised protectionist tools to reward Mr. Clinton’s union friends, it thought. Mr. Kantor, then the nation’s chief trade negotiator, had to convince the Mexicans that Congress would not ratify the deal without them.

“There was not a lot of space to negotiate,” he told me. “We could negotiate how to do it but not whether we would do it.”

Mr. Kantor invited the Mexican trade minister, Jaime Serra Puche, to watch the Senate pass the president’s deficit-reduction package. It made it, given the opposition of every Republican and some Democrats, only by the single vote of Vice President Al Gore. “When he saw that, he understood,” he said.