Elizabeth Warren’s 2020 Campaign Says It Raised $6 Million

Candidates must report their fund-raising for the first quarter to the Federal Election Commission by April 15, but campaigns can announce numbers before that deadline.

Based on information disclosed by campaigns this month, Mr. Sanders leads the Democratic pack with $18.2 million raised in the first quarter, followed by Ms. Harris with $12 million and Mr. O’Rourke with $9.4 million.

Pete Buttigieg, the mayor of South Bend, Ind., raised more than $7 million, Senator Amy Klobuchar of Minnesota raised more than $5.2 million and Senator Cory Booker of New Jersey raised more than $5 million, their campaigns have said. (Ms. Klobuchar solicited donations for the general election as well as the primary, so a portion of her total cannot currently be used.)

A New York Times article detailing some of Ms. Warren’s early fund-raising struggles, which posted online on the last day of the quarter, helped create an outpouring for Ms. Warren, handing her one of her best fund-raising days of the quarter, according to a Democrat familiar with her fund-raising.

Ms. Warren, who won her Senate re-election bid by a wide margin in November, has a big financial cushion because of the money she accumulated as a Senate candidate. Presidential candidates can make use of money they previously raised in federal campaigns, and Ms. Warren transferred $10.4 million from her Senate account to her presidential campaign, her team said. She ended the first quarter with $11 million in cash on hand, her campaign said.

On Wednesday, Ms. Warren also disclosed her 2018 tax returns, showing that she earned about $325,000 from her books last year on top of her Senate salary.

Ms. Warren had previously posted 10 years of her tax returns online, and she has called on her fellow presidential candidates to do the same thing. She has proposed a wide-ranging anticorruption bill that would require the disclosure of tax returns for the president, vice president and major party nominees for those offices.