“No,” Bernie Sanders responded in an April 2016 interview when asked by NBC’s Chuck Todd whether he thought the Democratic Party had been fair to him in his primary challenge against Hillary Clinton, the presumptive presidential nominee. “Look, we’re taking on the establishment. That’s pretty clear.”

Days earlier, on the eve of the Democratic primary in New York, the Vermont senator had accused the Clinton campaign of improperly subsidizing the former secretary of state’s presidential bid through the Hillary Victory Fund, the joint fuy vehicle her campaign set up with the Democratic National Committee and 32 state party committees. The Clinton camp forcefully dismissed Sanders’s accusation and argued that his attacks had “gotten out of hand.” “As Senator Sanders faces nearly insurmountable odds, he is resorting to baseless accusations of illegal actions and poisoning the well for Democratic candidates up and down the ticket,”Robby Mook, Clinton’s campaign manager, said.

Although he eventually campaigned for Clinton after she clinched the nomination, Sanders spent the next several months claiming that the primary system was “rigged” against him, only to be roundly dismissed by party leadership. But according to Donna Brazile, who served as the interim D.N.C. chairwoman after Debbie Wasserman Schultz’s ouster, Sanders’s accusations were hardly baseless. In her new book, Hacks, an excerpt of which was published Thursday by Politico, Brazile says she found concrete “proof” that the Clinton campaign stacked the deck: an August 2015 document outlining the “Joint Fund-Raising Agreement between the D.N.C., the Hillary Victory Fund, and Hillary for America” that effectively allowed Clinton to control the D.N.C.’s purse strings.

The agreement—signed by Amy Dacey, the former C.E.O. of the D.N.C., and Robby Mook with a copy to Marc Elias—specified that in exchange for raising money and investing in the D.N.C., Hillary would control the party’s finances, strategy, and all the money raised. Her campaign had the right of refusal of who would be the party communications director, and it would make final decisions on all the other staff. The D.N.C. also was required to consult with the campaign about all other staffing, budgeting, data, analytics, and mailings.