It’s true that small donors are, quite literally, giving billionaire-backed Super PACs a run for their money this election season, boosting candidates like Ben Carson on the right and Sanders on the left. Since it was founded in 2004, ActBlue has been working to bring more of these donors into the Democratic fold. In that time, the non-profit, which is backed by donations and gives its software tools to campaigns for free, has processed more than $850 million in donations for 11,000 Democratic candidates and committees.

But ActBlue’s impact has ballooned this year, thanks, in large part, to ActBlue Express. It’s not that it’s the only political donation tool on the market. There are plenty. But more often than not, they’re either dedicated to a single candidate or cost campaigns a lot of money. The key to ActBlue Express’s popularity—and its success—is the fact that aside from the fees credit cards companies charge, it’s free for campaigns and has been used for everything from the presidential elections to local school board races.

Now, some 1.8 million Democrats have voluntarily saved their information with ActBlue Express so that, for instance, someone who donated to a Congressman who’s using ActBlue could donate to a presidential candidate who’s also using ActBlue, without having to re-enter her personal information. And the Express database is growing exponentially. In just the last two months, Hill says, some 300,000 new donors have saved their information with Express.