Ripon, Wisconsin - Democratic presidential candidate Kamala Harris will rally Thursday with Liz Cheney, a staunch Republican opponent of Donald Trump, as both Harris and former president Trump hit crucial Midwestern swing states.

Trump is on the campaign trail in Michigan hours after his wife Melania added more spice to an already tense race by defending abortion, in stark contrast to her husband's position on the key issue.

Harris is heading to the symbolic birthplace of the Republican Party in Ripon, Wisconsin, with Cheney, the former congresswoman who has switched sides to back Harris along with her father, former vice president Dick Cheney.

Trump has chosen a deeply strategic venue, the rust-belt Michigan county of Saginaw that he won in 2016 and then lost to Joe Biden by a narrow margin in 2020.

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Current vice president Harris will be using her rally to reach out to Republicans whom Democrats hope are turned off by Trump's extreme rhetoric on subjects ranging from abortion to migration and democracy.

The conservative Liz Cheney was one of only 10 Republicans to vote to impeach Trump over the January 6, 2021 attacks on the US Capitol by Trump supporters trying to overturn his 2020 election loss.

Harris said in September she was "honored" by the endorsements of the Cheneys, saying they showed the need to "put country over party."

Liz Cheney was thrown out of the leadership of the House for her opposition to tycoon Trump.

Dick Cheney's support meanwhile came as a surprise from the former right-hand man to President George W. Bush.

Trump will be fighting for votes in Saginaw, one scene of the battle to win over the disaffected and mostly white working class in cities hollowed out by globalization.

Harris has a narrow lead in polls in Michigan but both candidates know that all the swing states could go either way and are hitting them relentlessly with just 33 days until the election.

The Trump campaign said his remarks were expected to focus on the economy, although most of his recent rallies have veered wildly off-topic as he attacks favorite targets like undocumented migrants.

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Trump and Harris remain neck-and-neck ahead of the election despite historic upheavals, including Harris replacing Biden as the Democratic nominee at the last minute in July and two assassination attempts against Trump.

Biden headed to Florida and Georgia on Thursday to view the devastation from Hurricane Helene, which has killed nearly 200 people across a swathe of southeastern states.

The Biden-Harris administration's response to the hurricane has threatened to become a new election issue – along with a US dockers strike and oil prices rising on fears of a Middle East war.