The former New York mayor, appearing in his first presidential debate, struggled from the start to address his past support for stop-and-frisk policing and longtime allegations of disrespectful behavior toward women.

“I’d like to talk about who we’re running against: a billionaire who calls women fat broads and horse-faced lesbians,” Elizabeth Warren said. “And no, I’m not talking about Donald Trump. I’m talking about Mayor Bloomberg.” She had the most speaking time onstage.

Go deeper: Here are six takeaways from the night, in which Bernie Sanders, who leads the polls, emerged relatively unscathed. We also fact-checked the candidates’ statements.

News analysis: Mr. Bloomberg’s uninspiring debate debut “risked underwhelming Democrats whose chief exposure to him in recent months has been through an inescapable ad campaign,” our political reporter Matt Flegenheimer writes.

The details: Watch highlights from the debate.

Perspective: Writers from our Opinion section ranked the performances.