With some 8.4 million registered voters and 15 electoral college votes of the 270 needed to win, Michigan is one of seven competitive US states that will decide the election.
It is part of the "Blue Wall" that is considered the Democrats' best chance of electing Harris, along with Pennsylvania and Wisconsin.
In Michigan, Harris and Trump are battling for voters that include a large Arab-American and Muslim population concerned about Israel's war in Gaza, and union workers worried about how electric vehicles could reshape the US auto industry, which is headquartered in Detroit, the state's largest city.
Michigan! I'll be joining — Michelle Obama (@MichelleObama) @KamalaHarris for a rally on October 26 – and I hope you'll tune in!It's up to all of us to do all we can from now until Election Day to support Kamala Harris and Tim Walz.Every single vote counts, and there's no time to waste! #DoSomething pic.twitter.com/vpeuOUEUiMOctober 18, 2024
Former President Trump has courted auto workers by pledging car-loan tax breaks and crackdowns on Chinese car sales.
Earlier this month, he made detrimental remarks about Detroit, a majority black city that Republicans have criticised for its crime rates, even as they dropped significantly in recent years.
He said of Harris: "our whole country will end up being like Detroit if she's your president".
Harris and Obama are expected to focus on the two contenders' policy differences on abortion rights, taxes, unions and tariffs.
Harris' rally will take place in the southern city of Kalamazoo, while Trump's will be in the Detroit suburb of Novi, about 210km away.
Harris is leading Trump nationally by a marginal 46 per cent to 43 per cent, a recent Reuters/Ipsos poll showed.
In Michigan, Harris leads by even less - 47.6 per cent to 47.1 per cent, according to opinion poll aggregator FiveThirtyEight.
Kamala Harris hopes the issue of abortion rights will energise people to vote on poll day. (AP PHOTO)
Democratic President Joe Biden, won Michigan by 150,000 votes in the 2020 election against Trump, a margin of less than 3 per cent, while Trump won by 11,000 votes in 2016.
Since the 2020 election, Michigan has instituted early in-person voting for the first time and begun permitting jurisdictions with more than 5000 people to begin processing and tabulating mail ballots eight days before the November 5 election day.
So far, 19.5 per cent of registered voters in Michigan, or nearly 1.42 million people, have voted, Michigan's State Department said on Friday.
Only 10,900 were in-person early votes, while the rest were returned absentee ballots.
Michelle Obama, the popular wife of former President Barack Obama, is the latest example of the Democrats leaning on star power in the final days of the election cycle.
Musicians Bruce Springsteen and Beyoncé have both campaigned with the vice president in recent days.
Trump, who will also travel to must-win Pennsylvania on Saturday, has brought in figures such as retired professional wrestler Hulk Hogan and musician Kid Rock.
In August, Michelle Obama spoke at the Democratic National Convention, where she tore into Trump, criticising his character and racist attacks that have targeted her and her husband in the past.
She taunted Trump for his reference on the campaign trail to unspecified "black jobs" that he said were being taken away from black Americans by migrants.
"Who's going to tell him that the job he's currently seeking might just be one of those 'black jobs?'" Obama asked.
Before Biden dropped out of the race in July, a Reuters/Ipsos poll showed that Michelle Obama led Trump 50 per cent to 39 per cent in a hypothetical match-up.
She has said repeatedly she does not intend to run for president.
