Delegates hold signs against the Trans-Pacific Partnership during the Democratic National Convention in Philadelphia in July. (Andrew Harrer/Bloomberg News)

It was perhaps the only point that Donald Trump and Hillary Clinton agreed upon during the entire debate: The Trans-Pacific Partnership, a mammoth trade agreement between the United States and 11 other Asia Pacific countries, is not a good idea.

“As bad as NAFTA,” Trump said, after earlier describing the North American Free Trade Agreement as “one of the worst deals ever made.”

Back in 2012, Clinton had described the TPP as the “gold standard” in trade agreements, but now says she changed her mind when she saw the fine print.

“Does it create jobs, raise incomes, and further our national security?” she said in Wednesday’s debate. “I’m against it now. I’ll be against it after the election. I’ll be against it when I’m president.”

The trade pact was the centerpiece of President Obama’s strategic rebalance to Asia, meant to underline American leadership in the world’s fastest-growing region — and balance China’s rise. If it falls apart, China is likely to be the big winner.

Congress has yet to ratify the agreement, and it would take considerable arm-twisting to get it through. With time running out for the Obama administration, and the U.S. political climate increasingly hostile toward free trade, the chances of the deal unraveling appear high.

It would be an enormous blow to U.S. credibility, and the prospect has been met with what Davin Chor, an economist at the National University of Singapore, calls “quiet exasperation” across the region.

That is, except in Beijing, which is not a party to the agreement.

“If the U.S. can’t ratify the treaty it has proactively negotiated, there’d be a vacuum,” said an Asian diplomat who spoke on the condition of anonymity while talking about a sensitive issue. And who would be looking to fill that vacuum? “China is watching closely,” he said.

While Clinton and Trump debated in Las Vegas, leaders from 14 Asian countries, plus Australia and New Zealand, were busy in the Chinese city of Tianjin on a 15th round of negotiations for an alternative trade deal, the Regional Comprehensive Economic Partnership, or RCEP.

It is a much less ambitious undertaking than the TPP, and negotiations have been slower than initially planned. Yet the very fact that the talks are being driven by China and exclude the United States is not lost on anyone involved.

“Time is not on our side, and the world is moving ahead,” Australia’s ambassador to the United States, Joe Hockey, warned in a speech at a forum in Honolulu in June. “And, as we speak, other deals are being advanced.”

“By ratifying the TPP, the United States will ensure it will continue to have a major leadership role in the Asia-Pacific region,” he said. “The cost of failure may well be too great to imagine.”

New Zealand’s ambassador to the United States, Tim Groser, said all the countries involved in the TPP had Plan B’s. “The tragedy would be that the Plan B’s we have would not include the United States,” he said Monday at an event in Washington, according to World Trade Online.

The agreement is supposed to reduce trade barriers and tariffs across 12 countries, including Australia, Japan, Mexico and Vietnam — but not including China. It covers a region that accounts for a quarter of the world’s population and 40 percent of its economic output.

The Obama administration argues the pact will spur U.S. growth and create jobs, boosting farm incomes by billions of dollars by opening up Asian markets while also raising labor, environmental and intellectual property standards across the region.

Critics say it gives too much power to big multinational companies and will undercut U.S. jobs and wages.

It was also supposed to reassure skeptics that Obama’s rebalance to Asia was more than an attempt to contain China militarily, and bind countries like Singapore, Vietnam and Malaysia into an economic framework where Washington played a leading role — to prevent them falling into China’s pocket.

Having spent political capital reassuring their own citizens about the deal, Asian leaders are watching closely.

“For America’s friends and partners, ratifying the TPP is a litmus test of your credibility and seriousness of purpose,” Singapore’s Prime Minister Lee Hsien Loong told business leaders in Washington in August.

In Tokyo this week, Japan’s parliament has been engaged in a heated debate on the merits of the pact, with Prime Minister Shinzo Abe urging approval of an “epoch-making deal” before the end of a special session of the Diet next month.

The Japanese leader has put huge store in the agreement to revive his nation’s sluggish economy, and he said this month that it was time for Japan to take the lead so that the whole deal didn’t go adrift, Jiji news agency reported.

The idea is to “send a message to Washington, D.C., and the United States, that we are waiting for you to come on board as quickly as possible,” said a Japanese foreign ministry official who spoke on the condition of anonymity because they were not authorized to be named. “But if the U.S. administration is not willing to join, there are competing regional free-trade agreements.”

Junichiro Sugawara of the Mizuho Research Institute said there was “frustration” in Tokyo that the Obama administration had not pushed harder to get the agreement ratified in the summer. “If it fails, it would be a major blow to Japan,” he said.

In Malaysia, Shankaran Nambiar of the Malaysian Institute of Economic Research said, “The impasse weighs heavily on the minds of policymakers,” partly because the deal had derailed earlier plans to finalize a U.S.-Malaysia free-trade agreement.

For those who worry about China filling the vacuum, there is a precedent. Congress created another vacuum, experts say, by failing to agree to reforms of the International Monetary Fund to give China and other developing nations greater say.

That led directly to China’s move to create the Asian Infrastructure Investment Bank, which came into being last year, and left some of Washington’s closest allies, including Australia and Britain, with little choice but to line up behind Beijing and join.

None of this is lost on foreign-policy thinkers in Washington. In August, eight former Republican foreign and security officials warned in Foreign Policy magazine that failure to ratify the trade pact would “cede to China the role of defining regional trade rules, and would be a body blow to U.S. standing and the U.S. economy.”

Secretary of State John F. Kerry said in a speech last month that failure to ratify would be a “giant step backward” for U.S. leadership in a region that would then ask itself: “Hey, if we can’t count on the United States, where else should we turn?”

In an interview, U.S. Trade Representative Michael Froman said the administration was “working around the clock” to win over members of Congress and give the TPP a chance of passage in the lame-duck session between November’s elections and January’s inauguration.

But Senate Majority Leader Mitch McConnell (R-Ky.) said in August that trade was a “toxic” issue at the moment, and any further discussion in Congress would have to be led by the next president.

Nor is reopening the negotiations to get a better deal for the United States a realistic option, experts say, with officials from other countries insisting the whole, complex deal would unravel if reopened.

Fifield reported from Tokyo. Luna Lin in Beijing and Yuki Oda in Tokyo also contributed to this report.

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Today’s coverage from Post correspondents around the world