One of Hillary Clinton’s top and most important advisers admitted on Wednesday that President Donald Trump’s opposition to the Trans-Pacific Partnership (TPP) deal—and Clinton’s waffling on it—was a vital reason why Trump pulled off his historic 2016 upset.

Philippe Reines, who also played Trump in Clinton’s debate-prep sessions, appeared on MSNBC’s The Beat with Ari Melber and was asked about the importance of the trade issue in 2016.

Melber asked: “Was trade and TPP a big factor in her loss? Yes or no?”

Reines, without hesitation, responded, “Absolutely yes.”

As soon as he entered the White House, Trump signed an executive order withdrawing the United States from the TPP, declaring that it was a “great thing for the American worker, what we just did.”

Breitbart News led the charge against the TPP, and Trump opposed the deal before he became an official presidential candidate. Clinton, who once called the deal the “gold standard” of trade agreements, waffled on the issue, especially when Sen. Bernie Sanders (I-VT) turned up the heat on the issue during the primaries. At the Democratic National Convention, some attendees held up anti-TPP signs, showing how much even some Democrats opposed the deal.

As Breitbart News’ Matt Boyle, who was arguably the most important reporter on the TPP issue, noted, “in May 2015—when many Republicans were in favor of TPP and before he announced his campaign—Trump told Breitbart News exclusively in an interview that the TPP was a ‘disaster’ of a deal.”

“I deal with foreign companies all the time. I do a lot of business with foreign companies and do well with foreign companies,” Trump told Breitbart News then. “The trade deal is a disaster for many reasons. Number one, we don’t have any good negotiators in our government. That’s possibly the single greatest reason—we don’t have our best and our brightest negotiating for us. That’s a real problem. Number two, and very, very importantly, it doesn’t take into consideration the currency manipulation because we get beaten in trade more by currency manipulation than any single other factor. So it’s not even discussed in the trade deal. They’re not addressing the number one cause of the unfairness which is the currency manipulation. China manipulates their currency so brilliantly and it’s very, very hard to compete. The other thing they do and they do it despite agreements is they make it impossible to sell product in their countries even after they sign an agreement so we need much stronger penalties if they continue to do that.”

In subsequent interviews with Breitbart News, Trump called the deal “insanity,” saying in a November 2015 interview, for instance, that the TPP “should not be supported and it should not be allowed to happen.”

“The deal is so bad because of the fact they don’t cover currency manipulation,” Trump said. “It’s the number-one weapon used by foreign countries to hurt the United States and take away jobs.”

In addition to illegal immigration, trade was what motivated key voters in states like Michigan, Ohio, Pennsylvania, and Wisconsin to vote for Trump. Top White House advisers like Gary Cohn, though, was on the other side of the issue, praising the “historic trade pact” in an op-ed that was published in a foreign publication.