ST. LOUIS - Republican presidential candidate Donald Trump vowed on Sunday to put his Democratic rival Hillary Clinton in jail if he wins the White House next month because she operated a private email server while US secretary of state.
Trump said he would appoint a special prosecutor to look into the matter because she had endangered national security while she served as President Barack Obama's chief diplomat from 2009-2013.
"You ought to be ashamed of yourself," Trump said to Clinton during a town-hall debate.
Clinton said it was good that Trump was not in the White House given his temperament, leading him to reply: "Because you would be in jail."
Trump also said he was embarrassed by a video in which he made obscene comments about groping women without consent, but dismissed it as "locker room talk."
Trump, who is facing a party rebellion over the 2005 video that emerged on Friday, said former President Bill Clinton had done worse to women.
"Mine are words and his are action," he said. He also accused Bill Clinton of going on the attack against women who had alleged sexual misconduct by her husband.
Clinton said Trump's comments showed he was unfit for the White House.
"He has said the video doesn't represent who he is but I think it's clear to anyone who heard it that it represents exactly who he is," Clinton said.
A flood of Republicans have withdrawn their support for Trump over the video showing the businessman, then a reality TV star, talking on an open microphone about groping women and trying to seduce a married woman.
The controversy has pitched Trump, 70, into the biggest crisis of his 16-month-old campaign and deepened fissures between him and establishment Republicans with only a month to go to the Nov. 8 election.
Trump met just hours before the debate on Sunday with three women who had accused Bill Clinton of sexual misconduct and a fourth woman who was a victim in a rape case that Hillary Clinton participated in as a defence attorney.
All four sat in the first row of the audience at the debate.
Before the debate, Trump had threatened he was going to attack Bill Clinton for his marital infidelities in response to criticism from Hillary Clinton that the Republican nominee is a misogynist who has a history of mistreating women.
Trump appeared with Paula Jones, who filed a sexual harassment suit against Bill Clinton in 1991, Juanita Broaddrick, who accused Bill Clinton of rape in 1978, and Kathleen Willey, a former White House aide who accused Bill Clinton of groping her in 1993.
None of the accusations was new.
Bill Clinton was never charged in any of the cases, and he settled a sexual harassment suit with one of the women, Paula Jones, for US$850,000(S$11,70,000) with no apology or admission of guilt.
Also at the event was Kathy Shelton, who was raped at the age of 12.
Hillary Clinton, a practicing attorney at the time, defended the rapist who ultimately pleaded guilty to a reduced charge.
Clinton's campaign responded to Trump's pre-debate event by calling it a "stunt" and a "destructive race to the bottom."