The control was given in exchange for a joint fundraising pledge by the Clinton campaign that helped fund the DNC through the election year, Brazile says.
"This was not a criminal act, but as I saw it, it compromised the party's integrity," she wrote in a book scheduled for publication next week, a portion of which was excerpted Thursday in Politico.
Throughout the campaign, the DNC and its then-chairwoman, Debbie Wasserman Schultz, fiercely denied any suggestion that the party was helping Clinton over other candidates. The presidential campaign of Sen. Bernie Sanders (I-Vt.) had criticized Wasserman Schultz for limiting the early primary debate schedule, allowing party money to be used for Clinton fundraising, and briefly cutting off Sanders's access to the party voter file shortly before the New Hampshire primary after a Sanders staffer inappropriately accessed information.
Some Democrats now say the arrangement is evidence that the concerns were valid. Ray Buckley, the chairman of New Hampshire's Democratic Party, said that he first learned of the agreement while serving as DNC vice chair in 2016. "The day that Donna discovered this, she called me and I almost passed out," Buckley said. "We were blatantly misled."
In response to the report Thursday, Sen. Elizabeth Warren (D-Mass.) said in a CNN interview that she believed the primary contest between Clinton and Sen. Bernie Sanders had been rigged. "This is a real problem," she said. "We have to hold this party accountable."
President Trump also jumped on the controversy with a tweet on Thursday night that suggested the Justice Department should investigate the "real collusion and dishonesty," even though Brazile and the Sanders campaign have not alleged criminal activity.
"Donna Brazile just stated the DNC RIGGED the system to illegally steal the Primary from Bernie Sanders," he wrote.
Trump said in an interview with Fox News Channel broadcast Thursday night that the Brazile allegations are "a major story."
"It's illegal, number one, and it's really very unfair to Bernie Sanders," Trump told Fox host Laura Ingraham. "I thought that was terrible."
The current leadership of the party said it would address the problem.
"One of my goals here, as DNC chair, is to make sure that the nominating process for 2020 is a process that's fair and transparent for everybody," DNC Chairman Tom Perez said in an interview with CNBC. "We're going to set the primary debate schedule well in advance of when we know which candidates will be there."
Charlie Baker, the chief operating officer of the Clinton campaign, said that in 2015 the campaign agreed to raise money for the parts of the DNC that were going to be most crucial to the general election, including data, research, communications and the like. The agreement also gave the Clinton campaign some say over personnel. If there was a vacancy for a position in one of these departments, the DNC had to consult the campaign on the three finalists but could make the final decision itself.
"We never tried to be presumptuous," Baker said. "We were literally trying to make sure the DNC had the resources it needed, whoever was the nominee."
The joint fundraising agreement allowed Clinton to raise hundreds of thousands of dollars from individual donors — money that was spread across state parties under federal campaign guidelines. Sanders had a different fundraising model, relying more on small-dollar donations directly to his campaign, and he told the DNC that his campaign was not interested in following the same program.
"The idea that the DNC was willing to take a position that helped a candidate in the midst of a primary is outrageous, and there is no justification for it," said Mark Longabaugh, a senior adviser to the Sanders campaign. "It gets back to the fundamental way that Bernie Sanders was running his campaign, which was to break the stranglehold of big money on politics."
Jeff Weaver, Sanders's campaign manager, said in an interview that their campaign was led to believe it had the same joint fundraising agreement as Clinton.
"We were not offered veto power on staff at the DNC, I can tell you that," said Weaver. "This was a laundering operation. They'd go to fundraisers, they'd get a $350,000 check from donors which was supposed to be divvied up. Instead of disbursing that money, they'd turn around and run a small-dollar fundraising to generate small contributions that went to the Clinton campaign."
In a September 2015 email obtained by The Washington Post, a lawyer from Perkins Coie, a law firm representing both the DNC and the Clinton campaign, wrote the Sanders campaign with a copy of what was presented as a "standard joint fundraising agreement."
"This is the same one we have used with other campaigns," wrote attorney Graham Wilson.
At the end of the same email, Wilson suggested that should the Sanders campaign raise "significantly more" money than was required to pay for the party voter file, then Sanders could have a say in how those funds would be used "to prepare for the general election."
"The DNC has had discussions like this with the Clinton campaign and is of course willing to do so with all committees raising funds for the Committee," Wilson wrote.
Weaver said the Sanders campaign decided early on to ignore the joint fundraising program and raise small dollars on its own to pay for access to the voter file. "Who are the wealthy people Bernie was going to bring to a fundraiser?" Weaver asked. "We had to buy the voter file right before the primaries."
After the election, the effects of the Clinton fundraising effort hit some state parties hard. Jane Kleeb, who took over Nebraska's Democratic Party in late 2016, discovered that the party had accrued $35,000 in debt for the Clinton campaign.
"Nebraska never even signed the JFA because we . . . didn't want to be a funnel for, essentially, money-laundering," Kleeb said. "And now we learn that a small group of establishment Democrats got to determine who our nominee was. That goes against everything that Democratic values are built on."
Kleeb, who along with Weaver is a member of the Democrats' post-primary "unity commission," said the party had made some amends under Perez's leadership. In his campaign to run the DNC and since, Perez has chastised Wasserman Schultz for turning the party into a vehicle for the presidential campaign.
After Brazile's book excerpt surfaced, state chairs began calling and emailing each other about a change to the DNC's rules and bylaws that would forbid any arrangement like the one Clinton got. Buckley and other DNC members suggested that the party should also give DNC members access to its budget, which would have made it clear much earlier how the joint fundraising agreement was affecting the flow of money.
"I will co-sponsor that amendment and vote for it," Buckley said. "There's so much reform that has to happen."
The 2015 agreement was struck at a time when the party's finances were in a dire situation. Two sources said that it was in danger of not meeting its payroll.
"The Clinton campaign had effectively taken control of the Democratic National Committee in the year before the nominating process began," said Tad Devine, the top strategist for the Sanders campaign. "They exercised their control through the use of the joint fundraising agreement."