Illinois Gov. J.B. Pritzker said that Vice President Kamala Harris needs to be cautious going into a debate with former President Trump in an interview on Monday.
"I don't think anybody should underestimate Donald Trump," Pritzker told CNN's Sara Sidner. "He has a won a couple of debates that he did. Certainly, people would say that he won the debate against President Biden a couple of months ago."
Trump and Harris are scheduled to debate on Sept. 10 hosted by ABC News.
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"We saw that he won the debate against Hillary Clinton when he ran the first time," Pritzker said of Trump. "He's not to be underestimated."
Pritzker said that while Harris is a "tremendous person with great capability" and communication ability, that might not be enough to beat Trump.
"We shouldn't be thinking that somehow Kamala Harris has a greater ability to win a debate than Donald Trump," Pritzker said. "They're going to come in as significant rivals with very, very different points of view."
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"I think getting those points of view across and making sure you're not getting flummoxed, frankly, by Donald Trump, will be an important thing for Kamala Harris," the governor added.
Harris' team has notably pushed to tweak the rules surrounding microphones during the debate, slated for Sept. 10, backtracking on formerly solidified agreements to have muted mics during the opposing candidate's speaking time.
The Harris campaign has still refused to sign off on the rules already agreed upon for the upcoming debate, which were initially supposed to mirror the guidelines outlined for the CNN debate held between former President Trump and President Biden in June.
"The memo sent by ABC is a draft set of rules that both campaigns need to sign off on and indicate agreement. We have not done so because we think both candidates have expressed a clear desire to have hot mics. Not clear why Trump staff is overruling their principal, who should be capable of making up his own mind," Harris spokesperson Brian Fallon wrote in an X post on Thursday.
The Harris and Trump campaigns did not immediately respond to a request for comment from Fox News Digital.
Fox News' Taylor Penley contributed to this report.