Obama calls Trump 'wannabe king' at Harris event

Harris swiped at Trump's past comment about being a dictator only on "Day One" and his more recent threat to use the military against political opponents.

"Donald Trump is increasingly unhinged and unstable," she said. "And in a second term, people like John Kelly would not be there to be the guardrails against his propensities and his actions. Those who once tried to stop him from pursuing his worst impulses would no longer be there, and no longer be there to rein him in."

Harris did not take any questions after she finished the brief remarks.

Harris, speaking at the vice president's residence, hammered Trump after his former chief of staff John Kelly's bombshell comments to the New York Times.

Kelly claimed Trump said he wanted generals like the ones Adolf Hitler had, and that, in his view as a retired general, the former president fell under the definition of a "fascist."

"It is deeply troubling and incredibly dangerous that Donald Trump would invoke Adolf Hitler, the man who is responsible for the deaths of 6 million Jews and hundreds of thousands of Americans," Harris said. "All of this is further evidence for the American people of who Donald Trump really is."

"The bottom line is this. We know what Donald Trump wants. He wants unchecked power," Harris added. "The question in the next 13 days will be: What do the American people want?"

With less than two weeks before Election Day, some 26.5 million Americans have cast their vote through early voting methods, according to data from the Election Lab at the University of Florida.

Mail ballots have been returned by 15.7 million voters as of Wednesday night, according to the data, with another 10.7 million voting early in person.

Several states are slated to begin early voting options in the coming days.

As Republicans attempt to encourage early voting, Trump called into Fox News host Brian Kilmeade's radio show to say he'll vote early, but he continued to show reluctancy about the practice.

"I'm very mixed on it. I mean, I'm OK with the Tuesday voting, which they like doing, Republicans like, and I'm also, I say, the main thing I say is vote," he said.

Trump also reiterated his baseless claims about cheating in this election cycle, saying it was his biggest concern when he was asked which of the battleground states worried him most.

"All of them. I mean, did they cheat? All of them? I mean, the biggest risk to me," Trump said. "I think we win it easily."

-ABC News' Lalee Ibssa