On a 237-197 vote, the House voted to grant permanent normal trade relations to Beijing and to end 20 years of turbulent annual reviews.
That was 19 more than the 218 votes needed for passage, a far more comfortable margin than either side had predicted.
Members stood on the floor watching transfixed as red and green lights on the electric tote board lighted up, and supporters broke into applause when the magic 218 number was surpassed.
"The Chinese market is opening. Somebody is going to have an opportunity to sell to this vast new market. The question is, who will be there when it opens?" asked House Speaker Dennis Hastert, R-Ill., who forged an alliance with Clinton to rally support for the measure.
The measure would open the way for American businesses to take full advantage of a series of market-opening concessions China has made to join the World Trade Organization.
Opponents said liberalizing trade ties with China would reward a brutal regime and cost American jobs.
"You can't have free markets without free people," complained House Minority Whip David Bonior of Michigan, the chief Democratic opponent.
The bill goes next to the Senate, where it has always drawn far wider bipartisan support than in the House. The measure has already won the 18-1 backing of the Senate Finance Committee and was expected to win full Senate approval early next month.
Opponents lost a last-ditch effort, shortly before the final vote, to send the legislation back to committee to modify it to revoke trade benefits if China invades or blockades Taiwan. That move was rejected 258-176.
Supporters said the president already has this power, and the move was just another way to kill the bill.
Clinton worked the phones throughout the afternoon to nail down wavering Democrats, supporters said. Texas Gov. George W. Bush, the likely GOP presidential nominee, also was busy trying to win over wavering Republicans.
Republican leaders had said they thought they could deliver 150 votes; they came up with 164. Democratic sponsors of the bill set a goal of 70-80; they produced 73.
Labor, a key Democratic constituency, waged one of its most intense campaigns ever against the bill. Nearly two-thirds of the House's 211 Democrats--including Minority Leader Richard Gephardt of Missouri--opposed it.
"When we stand up, things get better for human rights in China. When we stand down, things get worse," Gephardt told the House.
But the administration and the U.S. business community countered with their own member-by-member drive, engaging in some heavy horse-trading to shore up support.
Rep. Charles Rangel of New York, the top Democrat on the Ways and Means Committee and a senior member of the Congressional Black Caucus, opened the way for other Democratic defections when he came out in support of the bill last week.
Rangel said the current system of annual review amounted to little more than "barking at the moon."
"Let's break down these barriers," Rangel said in an impassioned speech. "Cutting off communication did not work for communist Castro. He's outlived 10 presidents. Don't let it happen in China."
Once the outcome became clear, Rangel and Bonior shook hands on the Senate floor.
Opponents--including some in the religious comunity and a coalition of environmental, human rights, and veterans organizations, in addition to labor--asserted the bill would condone human rights violations and make it easier for U.S. manufacturers to move factories to China and exploit low-wage workers.
"This is a government that has killed its own people," protested Rep. Joe Moakley, D-Mass.
Clinton's previous record on trade was mixed. Although Congress narrowly approved legislation establishing free trade with Mexico and Canada in 1993, it refused in 1997 and 1998 to grant him authority to make "fast track" decisions on trade agreements.
This bill would give China the same low-tariff privileges that the United States routinely accords its other trading partners. For the past two decades, Congress has granted China these benefits--previously called "most favored nation" status--annually, even after the 1989 Tiananmen Square crackdown.
The bill would also put in force a landmark market-opening pact negotiated with China last November as part of its entry into the World Trade Organization.