WASHINGTON (Reuters) - U.S. presidential contender Bernie Sanders raised $18 million in the second quarter for his White House run, his campaign said on Tuesday, putting his total behind 2020 Democratic rival Pete Buttigieg for the period.

FILE PHOTO - Democratic 2020 U.S. presidential candidate Senator Bernie Sanders attends a campaign event at George Washington University in Washington, D.C., U.S. June 12, 2019. REUTERS/Carlos Barria

Sanders, a U.S. senator from Vermont, also transferred $6 million from other campaign accounts to fund his presidential bid, campaign manager Faiz Shakir told reporters on a conference call.

Sanders and Buttigieg are the first among some two dozen candidates vying for the Democratic nomination to report fundraising numbers for April through June. Buttigieg, the mayor of South Bend, Indiana, raised $24.8 million from nearly 300,000 donors in the second quarter this year, his campaign said on Monday.

The Federal Election Commission’s quarterly deadline for reporting fundraising totals was midnight on Sunday. Campaigns must submit their financial reports by July 15.

Sanders, making his second bid for the White House after a losing 2016 run, led the Democratic field in fundraising in the first quarter by bringing in more than $18 million.

But he has been slipping slightly in polls in the last month and his rivals have stepped up their fundraising in the crowded race for the right to challenge Republican President Donald Trump in 2020.

Shakir rejected any predictions of doom, however, saying Sanders had his second-best fundraising day after the Democratic debates last week, bringing in nearly $2 million in one day.

Sanders has rejected holding big-money fundraising events like some of his rivals. Shakir said the grassroots, small-dollar nature of his fundraising showed the breadth of his support.

The average donation was $18, and 99% of the donations were under $100, Shakir said. The campaign ended the quarter with about $30 million in cash on hand, he added.

Shakir contrasted that approach with rivals like former Vice President Joe Biden, who has courted high-dollar donors.

“When you go into these high-dollar meetings, their support comes at a cost,” Shakir said.

Trump’s re-election campaign announced on Tuesday it had raised $54 million in the second quarter, after raking in more than $30 million in the first quarter.