By Fredreka Schouten and David Wright, CNN

(CNN) -- ActBlue, the online fundraising platform for liberal candidates and causes, helped drive more than $1.2 billion into federal campaigns in the midterm elections. That money fueled Democratic victories in the House and has left Republicans scrambling to build an equivalent powerhouse on the right.

The nonprofit ActBlue occupies a unique space on the political landscape, serving as a one-stop giving vehicle for virtually every candidate and organization on the left. More than 14,800 groups and candidates use the platform.

Adding in the money ActBlue helped send to liberal groups and non-congressional candidates, the online engine helped move a record $1.6 billion to Democratic candidates and causes in this cycle. The average donation: $39.67.

"Small-donor energy was everywhere," said Erin Hill, the executive director of ActBlue, which married technology with red-hot Democrat anger at President Donald Trump and his policies to smash records in the midterms.

"People wanted to do something constructive with their frustration" and "send a signal ... that they were coming for seats, and they had the resources to do that," she added.

Trump, a celebrity-turned-politician, saw big online small-dollar fundraising success in 2016. Nearly two-thirds of the money he collected from other individuals in his campaign came in amounts of $200 or less, federal data show.

But there's no central online fundraising clearinghouse in his party to help all Republicans. Instead, GOP candidates tend to rely on several for-profit vendors for those services.

"It's like a body of water with a dam, and the Democratic dam has got this big hole they can open and close and let water out," Josh Holmes, a Republican consultant and former top aide to Senate Majority Leader Mitch McConnell, said of ActBlue.

"Republicans have these little cylinders," he said. "When the water pressure is low, you can't tell much difference between Republican online fundraising and Democratic online fundraising. But when the water pressure is really high, like it was in 2018, there's a huge difference."

In the wake of last month's elections, party leaders are racing to catch up.

Casino magnate Sheldon Adelson, who donated more than $112 million with his wife, Miriam, to a constellation of Republican super PACs and groups to become the GOP's biggest donor in the midterms, has urged top Republican leaders to ramp up the GOP's online fundraising infrastructure.

A working group that includes Republican National Committee officials and House and Senate political aides already has reached "conceptual buy-in" on a plan to build a structure that allows greater back-end collaboration among the for-profit vendors, said a Republican strategist involved in the discussions.

But Matt Gorman, a former National Republican Congressional Committee official, said it may take time to close the online fundraising gap, given ActBlue's 14-year head start and the ingrained patterns of political giving among the GOP's small-dollar contributors.

Democratic low-dollar donors "are more likely to give to several different candidates across the country they know a bit about but are generally for the cause," he said.

"Republican low-dollar donors are more focused on the person. They will give, but to certain people," he said. "It's a cultural problem."

More than half -- 54.9% -- of the money from individual donors to Democratic House candidates in the midterms flowed through ActBlue, its data show. In the end, the party netted 40 House seats to seize the majority in the chamber, giving Democrats their best election results since Watergate.

Michael Malbin, executive director of the Campaign Finance Institute, said ActBlue's growing influence "is part of the story of nationalized politics."

It offered energized Democrats a way to turn their small money into big results, said Malbin, whose group tracks political fundraising.

"My friends who live in Massachusetts could give money in Georgia," Malbin said. "They knew very little about the governor's race or House candidates down there. They just knew these looked like OK people and they were in close races. And they were interested in national results."

The nonprofit has seen explosive growth since its founding in 2004 during President George W. Bush's re-election campaign -- when it processed less than $1 million across all federal races.

Two years later, the number had jumped to $16 million. By 2016, the last presidential cycle, it had hit nearly $695 million before nearly doubling to more than $1.2 billion in the 2018 election.

The group has seized on advances in technology -- the advent of one-click donating and Apple wallet, for instance -- to allow motivated donors to act quickly when candidates or causes catch their attention. Nearly 6 million maintain "express" accounts that store donors' payment information and addresses, making it easier to donate to multiple candidates over an election cycle.

The group's central role in Democratic fundraising means its constant testing and tweaks -- such as experiments to see whether enlarging or moving the "donate" button yields more contributions -- immediately benefit thousands of candidates, Hill told CNN.

Sheldon Cohen, a retired counselor who lives in Hopewell Junction, New York, used ActBlue to donate to more Democratic candidates than he can remember -- sending $10 or $25 at a time to Texas Rep. Beto O'Rourke's Senate campaign or to the re-election campaign of Pennsylvania Rep. Conor Lamb. (O'Rourke lost; Lamb won.)

Cohen, whose credit card information is stored with ActBlue, said he often sat on his computer, reading Twitter during the campaign and "if a candidate appealed to me I would send a few bucks here and few bucks there."

"It was money they couldn't raise in their own states," he said. "As a liberal, I felt like I was helping."