Bernie Sanders raised US$20 million (AU$28 million) in January 2016 itself, his campaign claims.

Sanders, who has to compete against Hillary Clinton’s huge financial backing, has insisted on trusting smaller donors rather than depending upon big corporates. According to the Bernie Sanders campaign, the Vermont senator has amassed a huge amount.

Sanders has over 770,000 donors, with an average of only $27. Overall, he has more than US$3.25 million (AU$4.6 million) contributions, a record for any presidential campaign until now.

It is widely known that Sanders has been critical of Clinton’s dependence on Super PACs and Wall Street donors. His campaign website asks for financial contributions with a reference to Clinton’s backers.

“We don’t have a super PAC — we don’t want one. But we still need money to keep getting the word out,” the website says. “Can you donate to our campaign?”

The contribution starts as low as US$10 ($14). According to the campaign’s financial disclosures on Sunday, it managed to raise US$33.6 million ($47.5 million) in the last quarter on 2015.

“As Secretary Clinton holds high-dollar fundraisers with the nation’s financial elite, our supporters have stepped up in a way that allows Bernie to spend the critical days before the caucuses talking to Iowans about his plans to fix a rigged economy and end a corrupt system of campaign finance,” Politico quotes campaign manager Jeff Weaver as saying.

When Sanders started his campaign in April 2015, not everyone thought he would be able to give such a tough competition to a seasoned politician like Clinton. He had to fight against a former secretary of state with an elaborated resume in politics.

Not only did he manage to stand shoulder to shoulder against Clinton, he is constantly narrowing the gap. According to the final Des Moines Register/Bloomberg poll in Iowa, he is just three points behind Clinton.

When asked which Democratic candidate cares most about “people like you,” 51 percent backed Sanders while Clinton got 37 percent. While both Sanders and Clinton are well-liked, the former US first lady has an edge over the 74-year-old as people are more enthusiastic about Clinton’s nomination.