The Trans-Pacific Partnership trade pact is regaining momentum despite the Trump Administration’s January decision to withdraw. Representatives of the remaining 11 TPP members met last month in Japan to push for ratification as early as November in the hope that Washington will rejoin. But even without the U.S., members stand to make significant gains.

A January study by Tokyo’s National Graduate Institute for Policy Studies makes the economic case for the smaller pact. Vietnam, originally expecting a 30% increase in exports under TPP by 2030, would still get a bump in textiles and apparel, as trade in those products is expected to grow $3 billion among the 11 member states. Malaysia would see a 20% increase in GDP due to reductions in nontariff barriers. Brunei would diversify its oil-dependent economy into biotech and agribusiness. New Zealand, Australia and Canada would actually enjoy bigger GDP boosts if the U.S. stays on the TPP sidelines. Their beef producers would secure preferential access to Japan’s market and take market share from American ranchers.

That shows how the Trump Administration has set back U.S. exporters by withdrawing from TPP. The U.S. is now seeking to renegotiate the North American Free Trade Agreement to obtain market-opening provisions that are part of the TPP. But Mexico and Canada don’t want to make concessions that were given in return for the broader benefits of TPP.

Keeping TPP alive hasn’t been easy. The lack of a U.S. market carrot led members to backtrack on some commitments. Vietnam, the only nonmarket economy in the pact, wants to freeze provisions on labor standards and intellectual property. But one positive surprise has been Japan’s leadership in the new negotiations. Tokyo is pushing members to reduce the number of provisions they want suspended to single digits by November.

Leaders seem to recognize that TPP is even more important in the Trump era. The common goal of the 11 nations is to convince the U.S. that TPP is essential to its influence in Asia. While Mr. Trump is unlikely to have a free-trade epiphany, the deal offers benefits to American exporters that the U.S. will struggle to secure on a bilateral basis. If the 11 remaining members hold out for a U.S. return, it’s possible that rational American self-interest will prevail over protectionist bluster.