Washington (CNN) Small-dollar donors contributed a record-breaking $297 million to liberal causes and candidates through ActBlue during the third quarter, the online fundraising platform announced Thursday.

The group expects fundraising through the platform to hit $3 billion by the end of the 2020 cycle -- a measure of Democratic enthusiasm ahead of next year's high-stakes White House and congressional races.

The nonprofit, which helped Democrats win control of the House of Representatives in 2018, said more contributions were made in the third quarter than in any other since ActBlue started in 2004. Small-dollar donors have now given more than $700 million this year alone, the organization said.

The record-breaking amount of small-dollar contributions comes as Massachusetts Sen. Elizabeth Warren and Vermont Sen. Bernie Sanders, who both swore off big-dollar fundraising, amassed the two largest third-quarter fundraising hauls. Both senators outraised candidates who have relied, in part, on larger donors to fuel their presidential campaigns.

The average donation size using ActBlue this past quarter was $28, and 1 million new unique donors used the platform. In the third quarter, 58% of donations were made using a mobile device, which is the highest percentage ever of donations made in a single quarter.

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