Ready for Hillary, the super PAC building a grass-roots campaign-in-waiting for possible 2016 presidential contender Hillary Rodham Clinton, raised more than $4 million in 2013, the group said Tuesday.

The haul came after the super PAC accelerated its fundraising in the second half of the year, holding events around the country with Clinton fans.

In all, Ready for Hillary raised $2.75 million in the second half of 2013, officials said Tuesday, more than double than during its first six months of existence.

The super PAC limited its ability to bring in large checks by voluntarily capping donations at $25,000. The move came as Clinton supporters fretted that the organization would end up competing for major donations with Priorities USA, another Democratic super PAC repositioning itself as a pro-Clinton vehicle.

Until that happens, though, donors have been flocking to Ready for Hillary as a way to register their early support for Clinton.

Super PAC officials stressed the group’s small-donor support Tuesday, saying that 98 percent of the 33,631 contributions were for $100 or less. Nearly 18,000 were for exactly $20.16, the entry price to get in fundraising events held in cities such as Los Angeles and Washington.

“Thanks to the groundswell of enthusiasm for Hillary’s potential run and the steadfast commitment of our supporters, we have exceeded our goals and are ahead of schedule in raising the funds necessary to build a grassroots army that can be activated the moment Hillary makes a decision,” said Ready for Hillary Executive Director Adam Parkhomenko in a statement. “This movement is unprecedented – not because of our staff but because of our supporters – and we will continue to build capacity across the country to put Hillary in the strongest position possible should she decide to run.”

Parkhomenko said that the donations were being “immediately reinvested in list-building, digital advertising and on-the-ground organizing to make sure that if Hillary decides to jump in the race, she will have as many supporters as possible lined up from the beginning ready to help her win.”