Both Vice President Kamala Harris and former President Donald Trump ramped up their rhetoric Friday as they both descended on one of the most hotly contested states in this election — Michigan.

At a rally in Grand Rapids, Vice President Harris took aim at Trump for refusing to do another debate, and questioned his fitness after a Politico report on Friday alleged that the former president was exhausted and backing out of interviews.

"His own campaign team recently said it is because of exhaustion," Harris said. "Well, if you are exhausted on the campaign trail it raises real questions about whether you are fit for the toughest job in the world."

Trump's campaign denied the report and hit back at Harris after touching down in Michigan.

"I want to see her do a cognitive test because she couldn't ace — because she wasn't born smart," Trump said.

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Both candidates held multiple events throughout the state. Harris gave remarks in Lansing and held another rally in Oakland County, while Trump stopped at a campaign office in Hamtramck, held a roundtable in Auburn Hills and rallied in Detroit.

On Saturday, Harris will campaign with two pop superstars — Lizzo in Detroit and Usher in Atlanta.

Trump will head back to Pennsylvania this weekend — he's set to hold a rally in Latrobe and a town hall in Lancaster.