Senator Kamala Harris of California dropped out of the Democratic presidential race on Tuesday after months of low poll numbers and a series of missteps that crippled her campaign, a deflating comedown for a barrier-breaking candidate who was seeking to become the first black woman to win a major party’s presidential nomination.

The decision came after weeks of upheaval among Ms. Harris’s staff, including layoffs in New Hampshire and at her headquarters in Baltimore, and disarray among her allies. She told supporters in an email on Tuesday that she lacked the money needed to fully finance a competitive campaign.

“My campaign for president simply doesn’t have the financial resources we need to continue,” Ms. Harris wrote. “But I want to be clear with you: I am still very much in this fight.”

The announcement is perhaps the most surprising development to date in a fluid Democratic presidential campaign where Ms. Harris began in the top tier. Her departure removes a prominent woman of color from a field that started as the most racially diverse ever in a Democratic primary, and raises the prospect that this month’s debate in Los Angeles will feature no candidates who aren’t white.
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Ms. Harris opened her campaign on Martin Luther King’s Birthday with a rousing speech in her hometown, Oakland, Calif., before an audience of 20,000 people, drawing comparisons to history-making black politicians like Barack Obama and Shirley Chisholm.