You've seen the signs, buttons and bumper-stickers. Heard the slogans. And listened to the candidates drop the acronym into speeches without a first-reference.
But what is it?
It stands for the "Trans-Pacific Partnership," a 12-nation trade agreement of Pacific Ring partners that was inked last February in New Zealand.
The United States signed the agreement with New Zealand, Australia, Canada, Japan, Malaysia, Mexico, Peru, Vietnam, Chile, Brunei and Singapore.
Billed by the U.S. Trade Ambassador as "the largest tax cut on American exports in a generation," the TPP is expected to sharply cut "nearly 18,000 individual taxes on the products American manufacturers make."
— USTR (@USTradeRep) July 19, 2016
President Obama is supportive of the agreement. The U.S. Congress has yet to ratify it.
TPP is billed by supporters as a pact that affords wage protections for workers in participating countries, safer working conditions as well as environmental regulations to protect wildlife and the earth against the dangers of climate change.
— USTR (@USTradeRep) July 22, 2016
For New York, the trade representative points out that grape juice, jewelry and aluminum would provide the best tax cuts on exports.
— USTR (@USTradeRep) November 10, 2015
But TPP has erupted into a major issue in this year's presidential election.
Expect to hear a lot more about it.
It's one of the few issues agreed upon by both Sen. Bernie Sanders, the former populist Democratic candidate from Vermont, and Republican nominee Donald J. Trump.
And, newly-minted Democratic nominee Hillary Clinton once called TPP "the gold standard" for trade, but now said she's opposed as the agreement is currently written.
[RELATED: Politifact finds Hillary Clinton was "distorting her previous comments" about TPP and the 'gold standard']
Why is it causing so much controversy?
Sanders calls TPP "a disastrous trade agreement" that will "hurt working families."
And, his supporters interrupted Monday's convention to let Democrats know that.
Sanders supporters now chanting "no TTP" while Rep Elijah Cummings talks voting rights. pic.twitter.com/mjyVQTXUOC
— Anthony Zurcher (@awzurcher) July 25, 2016
Trump repeatedly attacks the existing landscape as it relates to international trade, including TPP and NAFTA, the North American Free Trade Agreement signed during Bill Clinton's administration.
Neither TPP nor international trade is featured prominently under the "issues" section of Clinton's campaign website.
The issue blew up again early today after Virginia Gov. Terry McAuliffe, and long-time Clinton confidant, told CNN late Tuesday that he expected the Democratic nominee to reverse her current feelings on the issue.
A spokesman for McAuliffe later told Politico, however, that he was only expressing to CNN what he hoped she would do, if elected.
And Trump pounced on the issue again earlier today with one of his many tweets:
Just like I have warned from the beginning, Crooked Hillary Clinton will betray you on the TPP. https://t.co/eoNTWK6I8y
— Donald J. Trump (@realDonaldTrump) July 27, 2016
So, stay tuned.