In a bombshell piece for Politico, excerpted from an upcoming book, Donna Brazile, the former Democratic National Committee chair, outlines her search for evidence that the 2016 Democratic Party nomination process had been rigged in favor of Hillary Clinton—and her shock at finding it.

Brazile, who took over as interim chair after a leak of DNC emails published by WikiLeaks had taken down then-chair Debbie Wasserman-Schultz, begins the piece by relaying the promise she had made to presidential candidate Bernie Sanders to sniff out any proof of collusion between the Democratic Party and the Clinton campaign during the party’s primaries.

The leak already provided hints that the DNC had favored Clinton throughout the nomination process, but Brazile says she decided to “follow the money.” What she found was shocking evidence that, as many had suspected all along, Sanders never stood a real chance of becoming the Democratic Party’s presidential nominee, not because he wasn’t the better candidate, but because the DNC was quite literally in the Clinton campaign’s pocket.

Due to millions of dollars of debt incurred during the Obama campaign of 2012, the DNC, under Wasserman-Schultz’s lead, drew up an agreement that allowed Clinton campaign funds to funnel into the party’s coffers in exchange for control over major decisions.

Brazile writes,

When the party chooses the nominee, the custom is that the candidate’s team starts to exercise more control over the party. If the party has an incumbent candidate, as was the case with Clinton in 1996 or Obama in 2012, this kind of arrangement is seamless because the party already is under the control of the president. When you have an open contest without an incumbent and competitive primaries, the party comes under the candidate’s control only after the nominee is certain. When I was manager of Gore’s campaign in 2000, we started inserting our people into the DNC in June. This victory fund agreement, however, had been signed in August 2015, just four months after Hillary announced her candidacy and nearly a year before she officially had the nomination. I had tried to search out any other evidence of internal corruption that would show that the DNC was rigging the system to throw the primary to Hillary, but I could not find any in party affairs or among the staff. I had gone department by department, investigating individual conduct for evidence of skewed decisions, and I was happy to see that I had found none. Then I found this agreement. The funding arrangement with HFA and the victory fund agreement was not illegal, but it sure looked unethical. If the fight had been fair, one campaign would not have control of the party before the voters had decided which one they wanted to lead. This was not a criminal act, but as I saw it, it compromised the party’s integrity. … I told Bernie I had found Hillary’s Joint Fundraising Agreement. I explained that the cancer was that she had exerted this control of the party long before she became its nominee. Had I known this, I never would have accepted the interim chair position, but here we were with only weeks before the election. Bernie took this stoically. He did not yell or express outrage. … I urged Bernie to work as hard as he could to bring his supporters into the fold with Hillary, and to campaign with all the heart and hope he could muster. He might find some of her positions too centrist, and her coziness with the financial elites distasteful, but he knew and I knew that the alternative was a person who would put the very future of the country in peril. I knew he heard me. I knew he agreed with me, but I never in my life had felt so tiny and powerless as I did making that call. When I hung up the call to Bernie, I started to cry, not out of guilt, but out of anger. We would go forward. We had to.

The revelation comes shortly after Norman Solomon and several others wrote a report entitled “Autopsy: The Democratic Party in Crisis” that censures the DNC precisely for not moving forward from the 2016 election having learned any of the crucial lessons the Sanders’ campaign offered.

Brazile’s book, “Hacks: The Inside Story of the Break-ins and Breakdowns that Put Donald Trump in the White House,” is set to come out Nov. 7, one day shy of the anniversary of last year’s election.