President Obama has amassed a donor base of 3.1 million Americans in his bid for a second term, surpassing his total from four years ago, Obama campaign officials announced today.

An infographic circulated by the campaign on Twitter shows Obama drawing significant support from small-dollar and repeat donors.

Two million supporters have given $25 or less in aggregate, the campaign reports. More than 1.4 million have given more than once this election cycle.

Underscoring the president's support among women, the campaign said three women donated for every two men.

In 2008, Obama reported 3 million unique campaign donors.

President Obama has said the involvement of millions of grassroots supporters differentiates his campaign from that of GOP rival Mitt Romney.

Through June, the Obama campaign raised 39 percent of its total funds from donors who gave $200 or less in aggregate, according to the an analysis of Federal Election Commission data by the nonpartisan Campaign Finance Institute. Romney raised 15 percent of his funds from the same class of small-dollar donors.