In her first appearance on the campaign trail alongside Vice-President Kamala Harris, former First Lady Michelle Obama urged Americans to cast their votes to protect the country from the "dangers" of Donald Trump.
In a fiery speech in Michigan - a key battleground state - Obama said the election was "too close" for her liking.
At another event in Michigan, Donald Trump vowed to breathe fresh life into the state's automotive industry and met with Arab-Americans he said could "turn the election".
Polls show the two locked in a tight race in Michigan, with Harris holding an extremely narrow lead 10 days before the 5 November election.
The state, with 15 electoral college votes, could lend a deciding edge to either candidate.
President Joe Biden won Michigan by a narrow margin of 2.78% in 2020 - about 150,000 votes - helping to propel him to the presidency.
In 2016, the state went to Trump by an even narrower margin of 0.23% against Hillary Clinton.
Speaking to a crowd of thousands at an events centre in Kalamazoo, Obama made repeated jabs at Trump, pointing to what she termed his "erratic behaviour" and "obvious mental decline".
The bulk of her speech, however, focused on a "genuine fear" of how a Trump administration could impact abortion rights, telling an enthusiastic crowd of voters that she believes a failure to elect Kamala Harris could have deadly consequences.
Many abortion rights advocates have raised concerns that abortion bans have threatened women's lives by denying them life-saving medical treatment.
"I'm deeply concerned that so many people are buying into the lies of people who don't have our best interests at heart," Obama said, adding that "ugliness will touch all of our lives".
Harris largely echoed Obama's comments, and told young Generation Z voters she understands why they might be "impatient" for change.
"I want to tell you that I see you and I see your power," she said.
At his own rally in Novi, Michigan, Trump largely stuck to frequent campaign promises about immigration, energy and the economy.
He was also joined on stage by a number of Arab-American and Muslim community leaders, including Dearborn Heights Mayor Bill Bazzi.
"We are supporting Donald Trump because he promised to end war in the Middle East and Ukraine," Mr Bazzi said. "The bloodshed has to stop all over the world, and I think this man can make it happen."
Trump said he believes that the Arab-American voters can "turn the election" one way or another.
The state is home to the 'Uncommitted' movement, which does not support Trump, but has refused to endorse Harris for what they see as a failure to take a more firm stance against Israel during the war in Gaza, such as committing to a weapons ban.
At the Democratic rally in Kalamazoo, however, some voters said they were much more preoccupied with abortion rights and perceptions that Trump is "undemocratic", than they were about conflicts abroad.
Kelly Landon, a resident of Canton, Michigan, said that her primary motivation in this election was allowing female relatives to be safe and be in charge of their bodies and their own futures."
Ms Landon said, in her view, other issues are secondary to the health and safety of women, as well as "their right to live the way they want to live".
National polling averages tracked by the OceanNewsUK show Harris with a slight lead nationally, although with Trump narrowly ahead in five of the seven battleground states that could decide the election.
