WASHINGTON (Reuters) - Beto O’Rourke raised more than $6.1 million within 24 hours of announcing his candidacy for the 2020 Democratic presidential nomination, his campaign said on Monday, highlighting his fundraising prowess in a crowded field.

The former three-term Texas congressman’s haul put him at the top of a Democratic pack of more than a dozen candidates so far including Bernie Sanders, the independent U.S. senator who sought the party’s nomination in 2016. Sanders raised $5.9 million in the first 24 hours of his 2020 campaign.

O’Rourke kicked off his presidential campaign on Thursday with a video on social media and a three-day visit to Iowa, which will hold the first presidential nominating contest in February 2020.

O’Rourke gained national prominence from a 2018 U.S. Senate race that he lost. His underdog challenge to incumbent Texas Republican Senator Ted Cruz attracted capacity crowds and record fundraising. O’Rourke drew a record $38.1 million in one quarter - out of a total haul of $80 million - more than any other U.S. Senate race and more than three times Cruz’s total.

Sanders held the previous one-day record among 2020 Democrats and his campaign said he raised about $10 million by the end of his campaign’s first week.

Some other Democrats showed smaller initial totals. Senator Kamala Harris’ campaign said she raised more than $1.5 million in the first 24 hours. Her Senate colleague Elizabeth Warren drew more than $299,000 the day she launched her exploratory committee, Politico reported.

U.S. Senator Amy Klobuchar reported raising more than $1 million in her campaign’s first 48 hours, while Washington Governor Jay Inslee reported more than $1 million three days after entering the race.

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Democrats have sworn off big money in their challenge to Republican President Donald Trump, who began his re-election campaign this year with $19.2 million in cash.

Contributions for O’Rourke raised online came “without a dime from PACs, corporations or special interests, he received contributions from every state and territory in the nation,” his campaign said in a statement. PACs refers to Political Action Committees.

Warren became the first Democratic candidate to reject traditional means of campaign funding, saying she would not hold political fundraising events with pricey admission fees.

In April, all candidates must disclose how much money they raised in the first quarter.