His position in 2018 is vastly different. He is more vital to the Government, with his party as a full coalition partner, and himself as Foreign Minister and Deputy Prime Minister, and soon to be Acting Prime Minister.
In theory, New Zealand First could have opposed the deal under the "agree to disagree" provisions of the Cabinet manual.
The political reality is it would have been a whip with which to thrash the coalition, for its lack of cohesion, real or apparent, and the need for Labour to rely solely on National.
Second New Zealand First would have been thrashed for failing to back a deal which will undoubtedly benefit regional New Zealand.
The benefit is less than hoped for, even National would concede that. What trade deal isn't?
But the prospect of New Zealand being left out would have meant a significant disadvantage to our exporters, especially in primary industries, relative to other TPP competitors.
That would have left New Zealand First vulnerable to attack as it tries to become the party of provincial New Zealand.
As is, TPP will deliver New Zealand new free trade agreements and better terms of access to two wealthy countries, Japan, Canada, as well as Mexico, Vietnam and Peru.
New Zealand has existing trade deals with the other TPP partners, Australia, Singapore, Brunei, Chile, and Malaysia.
With the withdrawal of the United States from TPP, some of its hard-fought elements, such as extending copyright, have been suspended, making it more acceptable to skeptics.
Those changes would have happened with or without a change of Government in New Zealand.
But two other changes under Jacinda Ardern's Government have made it even more acceptable to former opponents: the ban on sales of existing houses in New Zealand to offshore non-residents, and narrowing the criteria under which Governments can be sued under investor state dispute settlement clauses.
Peters' support of the revised TPP, renamed the CPTPP (Comprehensive and Progressive Agreement for the Trans Pacific Partnership), coincides with the announcement that the last hold-out, Canada, has now deemed the deal acceptable.
Canada's failure to show up to the meeting in Vietnam in November for a pre-arranged signing ceremony infuriated other leaders, especially Japan's Shinzo Abe, who has been the de facto leader of TPP deal since the US withdrawal.
It is understood that since then, Japan has been playing hardball and Abe has been pressing for the deal to be signed in Chile with or without Canada.
Canada may have decided, like New Zealand First, that is it better to be on the TPP bus at the outset rather than left waiting for the perfect deal which, inevitably, will never arrive.