Speaking to supporters in Toledo, Ohio, Trump said the North American Free Trade Agreement signed by Clinton's husband, former President Bill Clinton, had led to the outsourcing of thousands of Ohio jobs to Mexico, a practice he vowed to stop if elected president on Nov. 8.
"We should just cancel the election and just give it to Trump, right?" he said. "What are we even having it for? Her policies are so bad."
Trump said he believed Clinton would seek passage of the 12-nation Trans Pacific Partnership, President Barack Obama's signature Asian trade deal, which she now opposes.
Trump's remarks came as the New York businessman tries to steady rocky poll numbers amid a series of controversies and self-inflicted wounds.
He has struggled to handle the fallout from the release of a 2005 "Access Hollywood" video that showed the then-reality TV star talking on an open microphone about groping women and trying to seduce a married woman. The video was taped only months after Trump married his third wife, Melania.
Trump said on Thursday it was "certainly illegal" for NBC to release the tape and he left open the option of seeking legal action against the network after the election.
Since the video's release, a series of women have accused Trump of groping them or kissing them without their consent. Trump has called the allegations "absolutely false."
The latest RealClearPolitics poll average showed Clinton with a nearly 6-point national lead over Trump, fuelled by declining support among women for his candidacy.
Trump, without evidence, has blamed his sagging poll numbers on a rigged election, and said the media had fixed the opinion polls in order to inflate Clinton's numbers.
Numerous studies have shown that voter fraud in U.S. elections is very rare, and a number of prominent Republicans have denounced Trump's claim that the system is unsound.
While Trump campaigned in Ohio, a plane carrying his running mate, Indiana Governor Mike Pence, skidded off the runway after landing at New York City's LaGuardia Airport on Thursday night. There were no injuries, the Pence campaign said.
STUMPING WITH FIRST LADY
Clinton on Thursday made her first joint campaign appearance with one of her most powerful supporters, first lady Michelle Obama, at a North Carolina rally to urge young people and women to vote.
Clinton, a former first lady who lost the 2008 Democratic nomination to then-U.S. Senator Barack Obama before becoming his secretary of state, praised Michelle Obama for standing up for the rights of girls and women worldwide, drawing a sharp contrast with her Republican rival.
"I wish I didn't have to say this. ... But indeed, dignity and respect for women and girls is also on the ballot in this election," Clinton told a crowd of about 11,000. "And I want to thank our first lady for her eloquent, powerful defence of that basic value."
Michelle Obama's stinging denunciation of Trump after a leaked 2005 video showed him making lewd remarks and bragging about groping women was seen by many as one of the campaign's most striking condemnations of the New York businessman.
Without naming Trump, Obama took him to task again in North Carolina, asking the crowd which candidate they wanted to represent their daughters from the White House.
"We want a president who takes this job seriously, and has the temperament and maturity to do it well. Someone who is steady. Someone who we can trust with the nuclear codes," Obama said.
"I would not be here lying to you: I believe with all of my heart that Hillary Clinton will be that president," she said.
Although Michelle Obama was critical of Clinton during the hard-fought 2008 Democratic nominating race, any trace of bitterness appeared long behind them. The two women showed an easy rapport. They embraced and smiled. Obama called Clinton "my girl" and made a point of telling the crowd they were tight.
"If people wonder: Yes, Hillary Clinton is my friend," she said.
Clinton promised to take good care of Obama's White House vegetable garden if she won and wistfully praised the athletic first lady's dancing skills. "One could only hope," Clinton said.
She also lauded Obama's work for children and military families and in what was perhaps a nod to African-Americans she hopes will vote for her in the state, said Obama had faced challenges she had not as a presidential spouse.
"Let's be real. As our first African-American first lady, she's faced pressures I never did, and she's handled them with pure grace," Clinton said to applause.
Although a sometimes reluctant campaigner, the first lady has thrown herself into the race, and the Clinton campaign has deployed her strategically to increase support among young people and blacks, with whom she is especially popular.
(Writing by Alana Wise and John Whitesides; Editing by Peter Cooney)
