Democratic nominee Hillary Clinton and Republican rival Donald Trump both landed in Cleveland, Ohio, on Labour Day as they launched into the home stretch of their general election campaigns, making appeals to unions and working-class voters.
A national holiday, Labour Day is celebrated on the first Monday of September in the United States.
Speaking to a crowd in Cleveland, Mrs Clinton said she and her running mate, Virginia senator Tim Kaine, would oppose attacks on unions and "unfair" trade deals, like the 12-nation Trans-Pacific Partnership, and "say yes to workers' rights and dignity".
She emphasised the importance of Americans working together and praised labour unions because they "work on a principle of solidarity".
She then turned her attention to Mr Trump, reminding the crowd of his track record and reputation as somebody who had "stiffed" others, meaning he had cheated them.
Trump has the edge in latest poll
Republican Donald Trump has a two-point edge over Mrs Hillary Clinton in the latest national survey of likely voters released yesterday, which showed the Democratic nominee's post-convention lead has largely evaporated.
Among those likely to vote on Nov 8, Mr Trump had 45 per cent support to Mrs Clinton's 43 per cent, according to the CNN/ORC survey. But among all registered voters surveyed, Ms Clinton led by three points, 44 per cent to 41 per cent.
Regardless of whom they supported, however, nearly six in 10 - 59 per cent - said they believed Mrs Clinton would win the election, while 34 per cent said Mr Trump would, reported the Politico website.
"One of his bankruptcies put 1,000 people out of jobs," she added.
She also raised his recent Twitter war with Mexican President Enrique Pena Nieto over who would pay for Mr Trump's proposed border wall and his hard-line stance on immigration as examples of him being "temperamentally unfit" to be the nation's commander-in-chief.
"Empty promises and racist attacks won't get your family a job... won't heal the divide in America," she added, while trying to suppress a serious coughing fit, which she blamed on Mr Trump.
"Every time I think about Trump, I get allergic," she joked.
Speaking to reporters at length - something she has avoided for months - Mrs Clinton also expressed alarm over reports of Russia's suspected interference in the United States elections by hacking into voter registers.
"We are facing a very serious concern," she told journalists on board her newly unveiled campaign plane.
"We have never had a foreign adversarial power being involved in our electoral process."
Also taking questions from the comfort of his private jet, Mr Trump clarified his views on immigration, saying that "to become a citizen, you are going to have to go out and come back in through the process. You are going to have to go out and get in line".
Mr Trump spent the day in Ohio engaging in some traditional retail politics, holding a round-table discussion with union members and labour leaders, visiting a diner and mingling with supporters at a county fair.
Out and about stumping for Mrs Clinton were Vermont senator Bernie Sanders in New Hampshire, US Vice-President Joe Biden in Pennsylvania, and former president Bill Clinton in Ohio and Michigan.
In his appearance in New Hampshire, Mr Sanders made his first speech in support of Mrs Clinton since he endorsed her in July.