Harris, the Democratic vice president, is scheduled to begin her day in Grand Rapids for a rally with other Democratic leaders.
She then goes to Lansing, where she'll speak at a United Auto Workers union hall and promote the White House's record of supporting domestic car manufacturing.
Her final event on Friday is a rally in Oakland County, which is northwest of Detroit.
Vice President Kamala Harris has failed to pick up some union endorsements in Michigan. (AP PHOTO)
Trump, the Republican former president, has his own event in Oakland County in the afternoon before holding a rally in Detroit in the evening.
Michigan is one of three "blue wall" states that, along with Pennsylvania and Wisconsin, will help decide the US president election.
Trump's event in Detroit will be his first one there since criticising the state of the city last week.
While warning what will happen if Harris is elected, he said that "our whole country will end up being like Detroit".
The city spent years hemorrhaging residents and businesses, plunging into deep financial problems, before rebounding in recent years.
One challenge for Harris in Michigan has been union support.
Although traditionally a Democratic bloc, she has failed to win key endorsements.
In addition, Arab American voters have been skeptical of Harris because of the White House's steadfast support for Israel's military operations in the Gaza Strip.
Michigan governor Gretchen Whitmer, a co-chair of Harris' campaign, said in an interview on Thursday that the expectation was always that "it was going to be a close election".
"People are like 'Oh it's so close'. And I'm like, have you not been listening for decades?" Whitmer said.
"Michigan is a divided state. And that's why we don't write off the reddest of areas on a political map. We show up."
Kent County, where Harris will start her day on Friday, leaned Republican for many years, and was won by Trump by 3 per cent in 2016.
But Biden won the county in 2020 and it has increasingly voted Democratic recently.
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