United States Democratic National Committee chief executive Amy Dacey has resigned following the publication of some 20,000 party emails on Wikileaks.
Her resignation comes after emails published by website Wikileaks exposed her questioning whether then-candidate Bernie Sanders was Jewish or an atheist.
The emails appeared to show Democratic National Committee (DNC) officials exploring ways to undermine Mr Sanders' campaign.
Ms Dacey's departure followed that of former party chair Debbie Wasserman Shultz, who resigned last week over the leaked emails.
DNC vice chairwoman Donna Brazile will serve as interim chair through the election.
Clinton pulls further ahead again
Meanwhile, a Reuters/Ipsos poll today showed Democratic presidential nominee Hillary Clinton's lead over Republican rival Donald Trump had jumped to 8 percentage points, up from 6 points four days before.
About 43 percent of likely voters favoured Mrs Clinton, 35 percent favored Mr Trump and 9 percent picked "other," according to the online poll of 1289 likely voters.
The poll had a credibility interval of 3 percentage points.
The bump for Mrs Clinton followed the Democratic National Convention in Philadelphia last week which painted an optimistic portrait of America, and came amid controversy over Mr Trump's comments about the parents of Muslim-American Army Captain Humayun Khan.
US President Barack Obama, a Democrat, today also questioned why the Republicans still supported Mr Trump, who he said was unfit for the post.
For his part, Mr Trump said he could not endorse House Speaker Paul Ryan, nor Senator John McCain, both of whom were facing Republican challengers in primary votes in their states ahead of the 8 November general election.
Both lawmakers had rebuked Mr Trump over his feud with Captain Khan's family.
House Republican Richard Hanna of New York said it was "not enough to simply denounce his [Trump's] comments," and said he would support Mrs Clinton instead.
Mr Trump also trailed Mrs Clinton in fundraising. The Democrat reported raising nearly $US90 million in July for her campaign and the Democratic Party, with more than half the donations coming from new donors.
Trump University case to continue through courts
Meanwhile, US District Judge Gonzalo Curiel rejected Mr Trump's pre-trial bid to win a lawsuit brought by students of Trump University who said they had been defrauded by its real-estate seminars.
Mr Curiel said in a written ruling there was a "genuine issue of material fact" as to whether Mr Trump knowingly participated in a scheme to defraud the students.
He said there was extensive evidence Mr Trump had not personally met, interviewed or selected Trump University instructors, although he represented they had been handpicked.