Former acting head of the Democratic National Committee Donna Brazile alleges in an upcoming book that the DNC conspired with Hillary Clinton to effectively hand her control of the national party during the 2016 primaries.

Politico Magazine published an excerpt of Brazile's book on Thursday with the headline, "Inside Hillary Clinton's Secret Takeover of the DNC."

Brazile writes that when she took over the DNC following the Democratic National Convention last year, she promised Clinton's primary challenger, Sen. Bernie Sanders (I., Vt.), that she would "get to the bottom of whether Hillary Clinton's team had rigged the nomination process."

"By September 7, the day I called Bernie, I had found my proof and it broke my heart," she writes.

Brazile claims that when she took over, she discovered that the DNC was badly in debt. As a result, her predecessor, Rep. Debbie Wasserman Schultz (D., Fla.), had struck a deal with the Clinton campaign allowing them to oversee DNC spending in return for Clinton fundraising for the DNC.

"The campaign had the DNC on life support, giving it money every month to meet its basic expenses, while the campaign was using the party as a fund-raising clearing house," Brazile says.

She writes that individuals who maxed out their $2,700 contribution limit to the Clinton campaign could write an additional check for $353,400 to the Hillary Victory Fund, the campaign's joint fundraising vehicle with the DNC. Most of that sum would go to the 32 state parties that were part of the Victory Fund, and then be transferred to the DNC. Money in the battleground states usually stayed in those states, but the other states funneled the money directly to the DNC, which in turn transferred the funds to the Clinton campaign.

"That victory fund was supposed to be for whoever was the nominee, and the state party races," Brazile remembers saying upon learning of this system. "You're telling me that Hillary has been controlling it since before she got the nomination?"

Gary Gensler, chief financial officer for Clinton's campaign, told her that it was true, and that otherwise the DNC would have collapsed.

Brazile writes that she finally discovered a copy of the agreement between the DNC and Clinton's team, which specified:

In exchange for raising money and investing in the DNC, 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 DNC also was required to consult with the campaign about all other staffing, budgeting, data, analytics, and mailings.

The agreement was signed by Amy Dacey, former CEO of the DNC, and Robby Mook, Clinton's campaign manager, in August 2015, a full six months before the first primary and a year before Clinton was formally the party's nominee.

Brazile writes that when she told Sanders about the agreement, the Vermont senator agreed to keep it silent to avoid splintering the party before the general election.

"When I hung up the call to Bernie, I started to cry, not out of guilt, but out of anger," she claims.