California Sen. Kamala Harris said she is dropping out of the Democratic presidential race, completing a surprising fall for a once-promising contender who drew 20,000 people to her campaign launch early this year.

Ms. Harris decided to exit from the race Monday after a discussion with her family and senior aides and after doing an audit of the campaign’s finances, according to a senior aide. She was one of only seven candidates to qualify for the party’s December debate, but she still didn’t see a path forward.

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