It was the second consecutive month that Romney collected more cash and underscores the challenge for Obama ahead of November. The totals include money raised by their respective political parties.
The news for Obama came as his campaign officials have publicly worried they were on track to lose the money race. Campaign manager Jim Messina, in an email to supporters just three days ago, said: "Their gap is getting wider, and if it continues at this pace, it could cost us the election."
Obama is fighting on two fronts to keep the presidency: On one hand, he faces Romney's own war chest, which pays for campaign operations. On the other, he has to push back against the hundreds of millions of dollars flowing to Republican-aligned super PACS, political action committees that have aired continuous attack ads aimed at Obama and his record.
Indeed, wealthy donors have been instrumental in helping Romney. When he broke fundraising records last month, Romney's campaign praised small-dollar donors it said made it possible. But it was actually a small number, often of wealthy donors, who gave an average of about $2,400 each, according to an Associated Press analysis.
Like Obama, Romney often touts the high percentage of donors who gave less than $250, underscoring the perception that a large, grassroots group of Americans wants him in the White House. Romney's campaign said that about 94 percent of 571,000 donors gave those amounts in June, or about $22 million.
But that leaves a little more than 34,000 responsible for the rest of the $83.8 million, the AP found. That's about $2,400 on average per person.
Just as first-class passengers pay the bulk of an airline flight's costs, wealthy donors to Romney and Obama often make the difference for campaigns. Even for Obama, who harnessed the power of small, grass-roots donations to help clinch the presidency four years ago, more than two-thirds of his supporters gave $200 or more.
Both men have broad geographic appeal, with contributions from all 50 states and the District of Columbia. Discounting small donors would ignore an important measure of support for the candidates, particularly as Romney is gaining on the president in terms of cash left in the bank.