Presidential hopefuls Hillary Clinton and Bernie Sanders ratcheted up their attacks in a bruising, final debate before next Tuesday's New York primary.
The Democratic race has turned increasingly negative in recent days as the candidates traded barbs about their qualifications for the presidency.
They also clashed on Wall Street banks, gun controls and the minimum wage.
Mr Sanders has won seven of the past eight contests, but Mrs Clinton holds a clear lead in race for the nomination.
The Democrats have largely avoided the personal attacks that have dominated the Republicans' debates.
But with so much at stake that changed in Thursday's debate.
"Does Secretary Clinton have the experience and intelligence to be president? Of course she does," Mr Sanders said at the debate. "But I do question her judgement."
Analysis by Anthony Zurcher, BBC North America Reporter
New York has a reputation for brashness and bellicosity, and it seemed that attitude may have rubbed off on the two participants in the Democratic debate in Brooklyn.
Practically from the opening bell, Hillary Clinton and Bernie Sanders went after each other's policy positions and records with a vigour that stood in stark contrast to the polite exchanges of past debates. Sure, they were both qualified to be president, they admitted, but both questioned their opponent's "judgment".
The former secretary of state knocked Mr Sanders off balance on gun control, quipping when he let out a chuckle during her response that 30,000 people dying a year is "not a laughing matter". Meanwhile, the Vermont senator once again bashed Mrs Clinton for her support of the 2003 Iraq War — tying it to the same kind of "mentality" that led to an ill-fated US intervention in Libya.
At one point moderator Wolf Blitzer tried to break up a heated exchange by warning that "if you're both screaming at each other, the viewers won't be able to hear either of you".
They kept talking. At this point in the marathon Democratic campaign, neither side can afford to let an attack go unanswered.
Grey line
Mr Sanders repeatedly criticised Mrs Clinton for her financial ties to Wall Street, particularly her paid speeches to an investment bank. He also faulted her for supporting the Iraq War.
Meanwhile, Mrs Clinton has questioned whether Mr Sanders has adequately thought out his policy proposals after he struggled to provide specifics during an interview with the New York Daily News.
"It's easy to diagnose the problem. It's another thing to do something about it," Mrs Clinton said.
The candidates' recent tensions were on display on stage. Mr Sanders mocked Mrs Clinton's responses at times while Mrs Clinton occasionally talked over her opponent.
Other highlights included:
Mr Sanders promised to release his past tax returns on Friday. but Mrs Clinton said she would not release transcripts of her paid speeches
Mrs Clinton said she would support a $15 federal minimum wage if it was passed by a Democratic Congress
Mrs Clinton aggressively criticised Mr Sanders' record on gun control, pointing out he voted to shield gun makers from legal liabilities
Mr Sanders spoke passionately about the threat of climate change. "Those little steps are not enough," he said of the policies of the Obama administration
Mrs Clinton defended her role in the US intervention in Libya; Mr Sanders faulted her for the breakdown in security in that country
Mr Sanders called for European allies to contribute more financial support to Nato, echoing sentiments from Republican front-runner Donald Trump
"We can't continue to be one sided," Mr Sanders said of America's role in solving the Israeli-Palestinian conflict
Mrs Clinton offered a full-throated defence of abortion rights, eliciting cheers from the crowd
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A resurgent Mr Sanders has won seven of the last eight contests, sparking a groundswell of enthusiasm from his supporters.
The Sanders campaign drew more than 25,000 people to a rally on Wednesday in Washington Square in Manhattan.
However, buoyed by earlier wins across the southern US, Mrs Clinton holds a sizeable lead in the number delegates needed to secure the nomination.
Many analysts believe that Mr Sanders needs to pull off an upset in New York to remain viable in the race.
Mrs Clinton, who represented the state in US Senate for two terms, holds a commanding lead in New York, according to recent polls.