Late Thursday night, President Trump tweeted, "Donna Brazile just stated the DNC RIGGED the system to illegally steal the Primary from Bernie Sanders. Bought and paid for by Crooked H...." in response to an explosive piece by former Democratic National Committee interim chair Donna Brazile.

In her forthcoming book Hacks: The Inside Story of the Break-ins and Breakdowns that Put Donald Trump in the WhiteHouse, Brazile took 2016 Democratic presidential nominee Hillary Clinton to task for rigging the DNC in her favor.

An excerpt of the book was published in Politico.

In the piece, Brazile alleges that before Clinton became the Democratic nominee, her campaign signed a joint fundraising agreement with the DNC and Hillary Victory Fund, in which her campaign would finance the DNC in exchange for oversight from the Clinton campaign.

Usually, the nominee doesn't take over fundraising until after they have accepted the nomination.

Brazile writes:

"The agreement — signed by Amy Dacey, the former CEO of the DNC, and Robby Mook with a copy to Marc Elias — specified that 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."

More:Elizabeth Warren agrees DNC was 'rigged' in Clinton's favor

When Brazile found out about the agreement, she said she called Clinton's former primary campaign rival, Bernie Sanders, to tell him the news.

Brazile writes that Sanders "took this stoically. He did not yell or express outrage. Instead he asked me what I thought Hillary’s chances were."

Brazile, previously resigned from her job as a CNN contributor after Wikileaks revealed she had passed debate questions on to the Clinton campaign.

Other tidbits from the excerpt: