Opponents of the North American Free Trade Agreement in the House picked up a key vote Monday and began framing a strategy for helping President Clinton recover from a defeat of the agreement.

Flanked by the second- and third-ranking Democrats in the House, Rep. Robert Torricelli, D-N.J., announced that the lack of human rights and labor freedom in Mexico would lead him to vote against the agreement Wednesday.He maintained that his vote was not in conflict with his "profound belief that free trade is a pillar of American prosperity" and called for a new trade agreement that includes labor and human rights reforms.

This idea, amplified in a recent speech by House Majority Leader Richard Gephardt, D-Mo., would set a broad number of conditions for Mexico before it would be granted preferential access to the U.S. market, supposedly similar to the conditions held out by the European Community before admitting countries as new members.

Mr. Gephardt, standing to the left of Mr. Torricelli, said he would favor a new grant of special negotiating authority for the president to secure this agreement if Nafta is defeated.

He went on to maintain that the Nafta, as negotiated by then-President Bush, was a desperate attempt to gain some edge during last year's election and not a serious attempt at a balanced trade agreement. "It was completed a month before the 1992 election . . . President Bush knew full well it could not be processed through the Congress," he said. "It was intended as a political boost."

Turning next to President Clinton, Mr. Gephardt argued that the president was forced to support the agreement and should be excused for sticking with it. The Nafta, Rep. Gephardt said, was "foisted on a Democratic president by a Republican president," and that "A Democratic president decided that he had to go through with it" as an agreement in good faith with Mexico.

Along with Mr. Torricelli and House Democratic whip David Bonior, D-Mich., Mr. Gephardt backed the new negotiation for a "Clinton Nafta." The majority leader said he would back a new grant of "fast track" negotiating authority to do it. Fast track, used for the Nafta, is so-named because it speeds trade pacts through Congress without amendments.

Mr. Gephardt's strategy for a Nafta defeat avoids some inconvenient facts that will hinder a new agreement. One is that the president came out for the Nafta in 1992, before it was "foisted" on him, and has said that supplementary agreements on labor and the environment are sufficient to address the concern of most Nafta opponents.

The White House picked up the vote of one key Democrat Monday, Rep. Norm Mineta of California, chairman of the Public Works Committee, which controls the kind of infrastructure spending that is the political currency of Congress.

Aides to Nafta opponents in the House say that most of the remaining undecided Democrats will come out in favor of the agreement, brought along by a combination of special interest deal-making and a more effective job by the White House of applying pressure to support their president.

More difficult is convincing about 20 undecided Republicans to go along with Mr. Clinton, these aides say.

At least two Republicans - Marge Roukema of New Jersey and Hamilton Fish of New York - came out in favor of the agreement Monday and more were expected after the House reconvened late Monday afternoon. Another undecided Republican, Scott Klug of Wisconsin, came out in favor Sunday.