President Donald Trump Friday said the American public "deserves" a federal investigation of Hillary Clinton and the Democratic National Committee over a joint fundraising agreement they allegedly signed in August 2015.
The DNC's former interim chairwoman, Donna Brazile, said Thursday in an excerpt from her book that she found "proof" that the 2016 Democratic primary was rigged in Clinton's favor, through a fundraising agreement that Clinton would raise money for the DNC and "control the party's finances, strategy, and all the money raised."
Trump has tweeted about the allegation eight times since Thursday, saying "Crooked Hillary bought the DNC & then stole the Democratic Primary." He also alleged it was illegal and worthy of an investigation from his own Department of Justice, though he provided no proof and Brazile said the agreement didn't violate any laws.
Trump's campaign is already under an investigation by special counsel Robert Mueller over whether it colluded with Russia ahead of the election. Three charges against members of Trump's campaign have already been made public, with one resulting in a guilty plea for lying to federal agents.
Asked Friday about whether he stood by his claim that his campaign never talked to Russia, Trump said "there was no collusion" and pivoted to the Clinton issue: "You want to look at Hillary Clinton and you want to look at the new book that was just put out by Donna Brazile where [Clinton] basically bought the DNC and she stole the election from Bernie" Sanders.
The fundraising agreement was unusual for an open seat, Brazile said. Months later, Clinton's chief challenger, independent Sen. Bernie Sanders, signed his own agreement with the party.
The DNC noted in a statement to NBC that joint DNC fundraising committees were created for both candidates, but Clinton was the only candidate to raise money for the party through one.
"The DNC must remain neutral in the presidential primary process, and there shouldn't even be a perception that the DNC is interfering in that process," Communications Director Xochitl Hinojosa said in the statement.
She did not immediately respond to follow-up questions about Brazile's allegations, or to questions about Trump's comments.
Trump appeared to acknowledge Thursday that his comments urging an investigation of a political opponent violate the American political norm of the president not intervening in law enforcement investigations.
"The saddest thing is that because I'm the president of the United States I am not supposed to be involved with the Justice Department," Trump said in a radio interview. "I'm not supposed to be involved with the FBI. I'm not supposed to be doing the kinds of things that I would love to be doing and I am very frustrated by it."
Yet Trump continued to tweet about it. "Everybody is asking why the Justice Department (and FBI) isn't looking into all of the dishonesty going on with Crooked Hillary & the Dems," he said.
And asked about the tweets on the Justice Department, Trump replied, "I'm really not involved with the Justice Department. I'd like to let it run itself. But honestly, they should be looking at the Democrats."
Trump also said that he is one of the people disappointed in the department and he's not sure whether he would fire Attorney General Jeff Sessions if the Democrats aren't investigated.
Sen. Elizabeth Warren, D-Mass., who said Thursday that she believed the primary was rigged in Clinton's favor, criticized Trump for changing the subject from Mueller's investigation into his own campaign.
"The DNC shouldn't play favorites. But that's a whole lot different from illegally conspiring with Russia. The FBI knows the difference," she tweeted, after Trump brought her up in a tweet, by using the racial epithet Pocahontas.
Warren continued, "Slurs, lies & trash talk won’t stop the FBI from doing its job. This isn't a dictatorship. It's our democracy. And it's stronger than you."
The Associated Press' Zeke Miller and NBC's Asher Klein contributed to this report