Nafta, signed by President Bill Clinton in 1993, helped lead to a boom in trade among the United States, Mexico and Canada. All three countries exported more goods and services to the other two, cross-border investments grew, and the United States economy has added millions of jobs since then. But of course not all those trends were attributable to Nafta, and the benefits were not equal: The United States had a small trade surplus with Mexico when the pact was signed, but that quickly became a trade deficit that has widened to more than $50 billion a year.
Critics of Nafta also point out that job growth in the United States does not account for the loss of jobs to Mexico or Canada; the A.F.L.-C.I.O. contends about 700,000 United States jobs have been lost or displaced because of Nafta.
Nafta was a significant victory for President Clinton after a difficult congressional battle, where he won support from just enough fellow Democrats to ensure passage. The votes were 234 to 200 in the House, and 61 to 38 in the Senate.
President Obama may yet win that kind of outcome. Working with Republican leadership in the House and Senate, he gained final approval for trade promotion authority, a critical step that allows the White House to present the trade package to Congress for a straight up-or-down vote, without amendments.
But the tortuous legislative process further soured relations with many fellow Democrats, as well as unions and progressive groups, who vehemently oppose the Trans-Pacific Partnership. Many Democrats said the president would have to address their concerns over labor and environmental standards and investor protections when he returns to Congress seeking approval of the trade deal.