Republican presidential hopeful Donald Trump staged a harsh attack on his Democratic rival Hillary Clinton on Wednesday, accusing her of corruption and dangerous incompetence as he tried to put his campaign back on track after recent setbacks.
In a speech in New York that Clinton's campaign called "nutty" and that was criticised by some Republicans, Trump argued that the former secretary of state is part of a political establishment that has cheated American workers through bad trade deals and endangered US national security.
Both candidates are seeking to overcome their high unfavourable ratings among voters at the November 8 election by painting the other as a villain who puts personal gain over the interests of less powerful Americans.
Even by the standards of modern presidential races, the sparring between Clinton, a former secretary of state and US senator, and brash businessman Trump has made for unusually acidic rhetoric.
"Hillary Clinton may be the most corrupt person ever to seek the presidency of the United States," Trump told a small crowd of supporters at a hotel he owns in Manhattan, accusing her of having run the State Department "like her own personal hedge fund."
Clinton's staff quickly dismissed that attack and others as "lies."
Trump read his speech from a teleprompter to curb his off-the-cuff comments but he pulled no punches. He said Clinton "has perfected the politics of personal profit and theft" and described her as "a world-class liar."
Republican Lindsey Graham, a US senator from South Carolina who has so far declined to support Trump, said he disagreed that Clinton may be the most corrupt person to have run for the White House, and challenged Trump to become more presidential.
“My advice to Mr. Trump would be to make the case that you have the temperament, knowledge and judgement to be president,” he said on CNN. “That’s the mountain you’ve got to climb.”
Trump's campaign has been distracted in recent weeks by racially-charged comments he made about a Mexican-American judge and the Republican's firing of campaign manager Corey Lewandowski this week.
The New York real estate mogul is trailing Clinton in most opinion polls, and campaign finance figures released on Monday show he has raised only a fraction of the amount Clinton has brought in, although Trump has said he is willing to loan his campaign more money.
In his speech, Trump repeated accusations that Clinton's decisions as America's top diplomat were influenced by donations to the Clinton Foundation and associated charities.
Clinton and her staff have denied this and similar allegations, dismissing them as politically motivated smears.
"The only thing Donald Trump offered today was more hypocritical lies and nutty conspiracy theories," Clinton spokesman Glen Caplin said.
The State Department has said it is not aware of any evidence of improper influence, although it has acknowledged that new donations from foreign governments should have been submitted to the department's ethics advisers for prior review but were not, in breach of an ethics agreement Clinton signed before taking office.
Trump attacked the Clinton Foundation for accepting millions of dollars from Saudi Arabia and other countries criticised by the United States for not protecting the rights of women and gay people. Clinton's husband, former President Bill Clinton, has said that accepting such funding is not an endorsement of everything a foreign government does.
Clinton added a pointed defence of the Clinton Foundation in a speech later on Wednesday.
"The Clinton Foundation helps poor people around the world get access to lifesaving AIDS medicine," she told cheering supporters in Raleigh, North Carolina. "Donald Trump uses poor people around the world to produce his line of suits and ties."
Trump also said Clinton had used bad political judgement in her four years as secretary of state, failing to stop the rise of Islamic State, keep strong sanctions on Iran or avoid chaos in Libya.
"Her decisions spread death, destruction and terrorism everywhere she touched," Trump said.
On Tuesday, Clinton delivered her own blistering attack on Trump, saying that putting him in the White House would be a disaster for the US economy.
On Wednesday, Clinton won the endorsement of former US National Security Adviser Brent Scowcroft, a Republican who served under Presidents Gerald Ford and George H.W. Bush.
A Reuters/Ipsos poll this week showed that 44.5 per cent of likely voters backed Clinton, while 35.5 per cent supported Trump.
Some of the accusations made by Trump on Wednesday appeared to contradict the public record.
He said Clinton would admit hundreds of thousands of refugees to the United States without any prior screening. But under the current process, refugees must wait months or years in foreign camps while US security agencies review their backgrounds, a system Clinton supports.
Trump said Clinton was sleeping "soundly" in her bed as a deadly attack unfolded in Benghazi, Libya, in 2012 in which four Americans were killed. State Department records show Clinton was in her State Department office when news of the opening assaults came through. She has said she later worked through the night on the US response.