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."
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.
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.
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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.