Bernie Sanders has raised $18.2m in the 41 days since he launched his Democratic presidential 2020 election bid, his campaign announced on Tuesday.

The Vermont senator is expected to post the largest early fundraising haul of more than a dozen candidates who have entered the crowded Democratic field so far.

Sanders’ campaign manager, Faiz Shakir, said it came from about 525,000 contributors giving about 900,000 individual contributions since Sanders announced his candidacy in February. He says the average donation was $20, and a majority of the contributors are under 39 years old.

The number of donations fell just shy of the campaign’s goal to reach 1m contributions by the end of the first quarter. But Shakir said the near-miss was an example of the campaign’s bold ambitions.

Candidates vying for the Democratic nomination to be US president began on Monday to disclose how much cash they were able to raise in the first quarter of the year – an early test of the energy and enthusiasm of a campaign.

California senator Kamala Harris said on Monday night she raised $12m since announcing her presidential bid in January. She earned donations from 218,000 individual contributions in the first quarter of 2019. Roughly 98% of Harris’s contributions were under $100, and 99.45% of her donors can contribute again, according to the campaign.

Pete Buttigieg, the relatively unknown millennial mayor of South Bend, Indiana, who launched a 2020 presidential exploratory committee two months ago, raised $7m in the first quarter of 2019 – an impressive haul for a candidate whose name many people are still only just learning how to pronounce. He earned donations from 158,550 donors with an average average donation of $36.35. Roughly 64% of the total amount are contributions under $200.

A significant number of grassroots, small-dollar donors is especially important in 2020, as a qualifier for the Democratic debates.

Other candidates in the race have yet to announce their fundraising numbers.

When Beto O’Rourke, a former congressman from Texas, entered the race, he raised $6.1m in a day. That followed Sanders, who raised $5.9m in his first day – and later disclosed he had raised $10m in a week.

Candidates are required by law to track and report all campaign donations. Donations collected between 1 January and 31 March must be disclosed by 15 April. Candidates are limited to collecting $2,800 from a single donor during the primary process.

The deadline will probably put a spotlight on those who have had difficulties raising money, including New York senator Kirsten Gillibrand, who has struggled to gain any traction in the polls. Media outlets have reported that she has been less than successful in finding financial backing.

The Massachusetts senator Elizabeth Warren announced earlier this year that her campaign would not hold any formal fundraising events and instead rely solely on “small-dollar” donations, or contributions collected online.

With such a crowded field – more than 15 Democrats have announced they are running – fundraising abilities have become an early way to prove to donors and potential supporters that a candidate is viable.

The Democratic National Committee has said a candidate must have raised money from 65,000 different donors in order to qualify for the first Democratic TV debates to be held in Miami on 26-27 June.

Associated Press and Reuters contributed to this report

