Democratic presidential candidate Sen. Bernie Sanders (D-VT) jokes around as he speaks during a campaign rally at Bonanza High School on February 14, 2016 in Las Vegas, Nevada.

Sen. Bernie Sanders' campaign said it raised $5.9 million from 223,000 donors within the first 24 hours of his 2020 presidential campaign.

With an average donation of $27, the Vermont independent's haul shows the power of small-dollar donations, which have become increasingly critical for Democrats looking to shore up grassroots support and shun corporate funds.

Sen. Kamala Harris of California previously announced raking in $1.5 million from 38,000 donors within the first 24 hours of announcing her presidential bid last month. Other candidates have not provided first-day funding information.

Sanders launched his campaign on Tuesday. The decision followed months of speculation that the senator would jump into the race after the surprising success of his insurgent 2016 bid, when he became the runner up behind Hillary Clinton.

In 2016, Sanders raised $1.5 million in the first 24 hours and went on to raise 58 percent of his campaign funds with individual contributions of less than $200, according to data from the Center for Responsive Politics. By contrast, small-dollar donations made up just 19 percent of Clinton's campaign funds.

"Sanders demonstrated a level of grassroots support of unprecedented size and excitement, signalling the strength of the movement set on winning the Democratic nomination, defeating Donald Trump and creating a government that works for all Americans," his campaign said in a statement Wednesday announcing his first-day fundraising numbers.

Sanders joins a crowded Democratic primary field, including Harris and fellow Sens. Elizabeth Warren, Cory Booker, Kirsten Gillibrand and Amy Klobuchar. Former HUD Secretary Julian Castro and South Bend, Indiana, Mayor Pete Buttigieg, among others, are also aiming for the party's nomination.

Sanders received donations from all 50 states within the first hour of his campaign. "Powerful special interests may have the money, but we have the people," he tweeted on Tuesday.

Sanders tweet

In a move to renounce the influence of big businesses, Sanders and other Democratic contenders have pledged to reject donations from corporate PACs. A similar trend prevailed in the 2018 midterm elections.

"We're not accepting a penny from corporate PACs or federal lobbyists, which means your donations really do make a difference," Harris said in a tweet.

Harris tweet

The surge of small-dollar donations in the 2020 campaigns can be partly attributed to ActBlue, an online fundraising platform for Democrats used by both Sanders and Harris. ActBlue helped candidates raise over $1.6 billion during the 2018 election cycle alone, with a $39 average contribution. On Sanders' fundraising page, the suggested donation amount starts at $3.

Sen. Elizabeth Warren, D-Mass., pulled in over $299,000 online the day she launched her presidential exploratory committee, according a Politico report citing a Federal Election Commission filing. A Politico analysis of ActBlue data showed more than 8,000 donations were collected for the senator on Dec. 31, working out to an average donation of about $37.

Warren officially announced her presidential bid on Feb. 9. The campaign did not release funding information for that day's take.