Republican presidential candidate Donald Trump tried to make the case that he’d do more to help women from the White House than Democratic rival Hillary Clinton, a lifelong champion of women’s rights who would become the nation’s first female president.

"My opponent likes to say that for decades she’s been fighting for women, that she’s been fighting for children.

Why, then, are 70 million American women and children living in poverty or on the brink of poverty in our country?" Trump asked a rally crowd in Roanoke. "For years she’s been doing this and she’s done nothing."

The appeal came hours after Trump threatened on Twitter to invite a woman who’d had an affair with Clinton’s husband, former President Bill Clinton, to sit in the first row at Sunday’s presidential debate. The Clinton campaign had invited Mark Cuban, a fellow billionaire and Trump rival, to the debate.

"If dopey Mark Cuban of failed Benefactor fame wants to sit in the front row, perhaps I will put Gennifer Flowers right alongside of him!" Trump said.

Trump’s campaign officials did not respond to requests for comment on Saturday’s remained unclear whether Flowers would actually attend.

Clinton’s campaign spokeswoman Jennifer Palmieri responded: "Hillary Clinton plans on using the debate to discuss the issues that make a difference in people’s lives." She added: "It’s not surprising that Donald Trump has chosen a different path."

Trump has been criticised throughout the campaign for crass comments he has made about women in the past, including insults about their physical appearance.

Clinton’s campaign has tried to capitalise on those comments, including with a new add that features images of adolescent girls looking at their reflections as audio of Trump’s comments play.

The tweet on Saturday underscored the challenges Trump faces as he attempts to close his deficit among female voters, whom polls show favour Clinton by significant margins.

Trump had all but ignored issues like child care and maternity leave until the Republican National Convention when his daughter, Ivanka, suddenly said her father would work to provide affordable childcare for women.

Clinton, on the other hand, released a policy a year ago and has spent much of her life advocating for women and girls.

After graduating from law school, Clinton worked for the Children’s Defense Fund.

She also co-founded the Arkansas Advocates for Children & Families early in her career and delivered a seminal speech as first lady declaring that "women’s rights are human rights." As secretary of state, she stressed the importance of women’s rights in of US foreign policy.