U.S. President Donald Trump is reconsidering membership in the Trans-Pacific Partnership trade agreement. If he follows through, it would constitute the most significant policy reversal since he took office. As welcome as this shift is, it is by no means guaranteed: Not only must Trump decide to go through with the membership bid, but the 11 signatories, which only recently agreed on a revised text, must then reopen the treaty for negotiations with Washington. U.S. membership in the TPP — now the Comprehensive and Progressive Trans-Pacific Partnership (CPTPP) — is much desired but not at the price of a weakened and diluted deal.

For Trump, no agreement better symbolized U.S. failure in trade policy than the TPP. In the 2016 campaign he excoriated President Barack Obama for negotiating the deal, at one point tweeting "The Trans-Pacific Partnership is another disaster done and pushed by special interests who want to rape our country. ..." One of the first executive orders he signed as president withdrew the United States from the agreement.

Yet rather than tear up the deal, the remaining 11 countries — Australia, Brunei, Canada, Chile, Japan, Malaysia, Mexico, New Zealand, Peru, Singapore and Vietnam — driven in no small part by Prime Minister Shinzo Abe, renegotiated the draft, removing many of the U.S. demands. That revised treaty was agreed and will go into effect when it is ratified by six of the signatories. In its current state, the CPTPP countries represent about 500 million people, and account for more than 13 percent of the global economy with a total GDP of $10 trillion. U.S. membership would boost that to 40 percent of global GDP, topping $30 trillion.