Free trade advocates are betting the United States will approve the TPP this year, despite trenchant political opposition to the pact.
The delegates gather after the signing ceremony Photo: MFAT
American support for the controversial deal to set up a free trade zone covering 40 percent of world trade and 800 million people is crucial - without it there's no deal.
But it's been under political fire from all sides - Democrats and Republicans have criticised the agreement for different reasons as a bad deal for the US, while the two main presidential hopefuls, Donald Trump and Hillary Clinton, have also condemned it.
But the executive director of the Asian Trade Centre in Singapore, Deborah Elms is hopeful the many years of negotiations will not be wasted.
"The few sensible people left in the room recognise that the odds of approval after that [November's elections] are not promising, and I think there are a number of people who've realised that it needs to get done," Dr Elms said.
Dr Elms and other TPP supporters are banking on Congress backing the TPP in the period between elections in November and mid-January - the so-called lame duck period.
"The lame-duck session is one where all rules don't apply. Lots of unpopular things get done in the lame-duck period, and I think in this particular lame-duck period TPP is the first thing on the agenda of unpopular things that will get done."
A visiting trade expert and TPP opponent Jomo Kwame Sundaram states it more baldly.
Dr Jomo said the lame-duck period allowed the Republicans to deny President Barack Obama any political credit from TPP, and enhanced the chances of outgoing politicians to find work.
"That's the time politicians who have lost in the Senate or Congressional races have to think about their post-retirement plans. And that concern alone tends to fixate the mind, " Dr Jomo said.
But another TPP opponent, Auckland law professor Jane Kelsey places the odds of a lame-duck vote as next to zero.
Professor Kelsey argues Republicans have continued to play hardball in demanding the monopoly protection period for next generation drugs called biologics will be beefed up from 5 to 12 years.
"The gatekeeper to that, (Republican Senate Finance Committee chairman) Orrin Hatch, has just upped the ante on it. So, unless he's satisfied, he has said he won't allow it into the Congress for a vote during the so-called lame-duck period," Professor Kelsey said.
TPP supporter and New Zealand International Business Forum executive director Stephen Jacobi has a warning for American business wanting to rewrite the TPP to their advantage.
"None of us are entirely happy with the outcome in TPP. In New Zealand we certainly aren't for a number of reasons in relation to dairy products for example. But we think this was the consensus agreement that was reached and it needs to be done now."
The TPP overcame considerable odds to reach agreement in October 2015 after five-and-a-half years of negotiations.
Whether that track record can be maintained as the controversial deal tiptoes through the complex minefield of US politics remains to be seen.
Certainly no one's counting on the TPP tripping up just yet.
