ActBlue, the online Democratic fundraising platform, announced Thursday that small-dollar donors gave over $1 billion in 2019. In the fourth quarter, donors made the most contributions of any quarter in ActBlue’s history, raising $343 million.

The amount also represents a large uptick from the same quarter in previous years. Roughly $168 million was donated in the fourth quarter in 2017 right before the midterm elections, and just $75 million was donated in the same quarter in 2015 before the last general elections in 2016.

Over the course of the year, 6 million individual donors made 3 million contributions through the platform — a record number of donors and contributions for ActBlue. Of the 6 million donors, half were new to ActBlue. In the fourth quarter, 11.2 million contributions were made, the most in any quarter.

“Our record-breaking Q4 indicated what we saw in all of 2019: unprecedented grassroots engagement and growth of the small-dollar donor movement, which we only expect to increase from here,“ said ActBlue Executive Director Erin Hill. “Our nominee will need at least half of their funds from grassroots donors if they want to beat Donald Trump. Based on what we saw last year, the eventual Democratic nominee will have an army of grassroots donors behind them.”

Grassroots fundraising is one of the qualifying factors to make it on to the debate stage, as Democrats have increasingly turned to small-dollar donors to pad their war chests. Presidential candidate Bernie Sanders is leading the Democratic field in Q4 hauls, bringing in $34.5 million. He was followed by Mayor Pete Buttigieg who pulled in $24.7 million. Sen. Elizabeth Warren raked in $21.2 million in total contributions, a drop from her third quarter figures.

The average donation size for these candidates is often small. For 2019, ActBlue’s average contribution size was $30.50. Over Q4, the average contribution size was roughly the same.

While the number of contributions continues to increase, the size of the donation has fallen. In the fourth quarter of 2017, the average donation size was just over $38.

The Trump campaign continues to handily surpass the Democrats in fundraising totals.

His campaign announced that in the fourth quarter, the president pulled in $46 million. That’s a boost from his third-quarter haul, which saw the Trump bring in $41 million. Trump starts the year with over $100 million cash on hand.

Republicans’ answer to ActBlue, WinRed didn’t fare as well — it raised some $70 million in the fourth quarter for Republican candidates. The figure represents a more than 100% increase from the previous quarter, when WinRed pulled in just over $30 million.