WASHINGTON (Reuters) - U.S. Senator Amy Klobuchar raised more than $5 million during the first seven weeks of her 2020 White House bid, with more than $3 million left over from her Senate campaign, leaving her with total cash on hand of about $7 million, her campaign said on Monday.

FILE PHOTO: Democratic 2020 U.S. presidential candidate and U.S. Senator Amy Klobuchar (D-MN) speaks at the Center for American Progress (CAP) Action Fund forum in Washington, U.S., March 5, 2019. REUTERS/Jim Young/File Photo

Klobuchar’s first quarter fundraising total is considerably less than others among the more than 15 Democrats who have announced they are running for the party’s 2020 presidential nomination.

Senator Bernie Sanders leads the pack, raising about $18 million during the first six weeks of his presidential run, his campaign said. Senator Kamala Harris raised $12 million during the first three months of 2019, according to figures released by her campaign.

Pete Buttigieg, the mayor of South Bend, Indiana, who recently saw a bump in opinion polls but is still considered a long-shot, announced last week that he had raised $7 million during the first quarter.

Beto O’Rourke, a former U.S congressman from Texas, raised $9.4 million in the first 18 days of his bid for the presidency, his campaign said.

The campaign of Senator Elizabeth Warren, who has sworn off high-dollar fundraisers to focus on grassroots donations, said she hit her first-quarter fundraising goal but has not yet released a figure.

Fundraising is an early way to prove to donors and potential supporters that a candidate is viable.

Grassroots fundraising is also one of the qualifying criteria for the Democratic primary debates. Candidates can qualify if they have 65,000 unique donors, along with a minimum of 200 donors per state in at least 20 states.

Klobuchar’s campaign said the average online grassroots contribution was $40 and that 85 percent of all donors gave less than $100.

Presidential candidates are required by law to report all campaign donations. They cannot accept more than $2,800 from a single donor during the primary race.

The campaigns’ first quarter fundraising reports are due to the Federal Election Commission by April 15.