Winslow Townson/AP Photo

For the third consecutive month, the Obama campaign spent more than it raised, assumed new debt and substantially depleted its cash-on-hand reserves, according to the organization's Federal Election Commission filing for July.

Obama for America collected $49.1 million between July 1 and 31 - a modest increase over June and on pace to match the president's fundraising record of $746 million from four years ago.

But a rapid summertime expansion of grassroots organizing operations in swing states and an aggressive advertising blitz against rival Mitt Romney has begun to drain resources. Obama for America spent $58.8 million over the same period, according to the filing.

The top five expenditures last month were media buys ($39 million), online ads ($8.7 million), payroll ($2.9 million), payroll taxes ($1.2 million) and polling ($900,000).

Obama's available cash on hand fell $10 million in July from $97 million to $87.7 million. Debts owed by the campaign rose to $2.8 million.

Meanwhile, the Romney campaign and affiliated groups are on track to out-raise and out-spend Obama with an expected $1 billion on advertising.

"I will be outspent in this election. And we will not win the ad wars on TV and radio - right now, the other side is outspending us on TV by at least 2-to-1 in most battleground states," Obama said in an email to supporters earlier this month.

"That's OK. But only if we're able to keep the spending gap close enough so that our investments in a truly grassroots campaign pay off," he said, making an appeal.

Joint fundraising accounts with the Democratic National Committee will help keep Obama competitive with Romney. The Obama Victory Fund raised $30.4 million in July. The party itself reported raising $9.9 million.

All official entities raising money for a second Obama term had a combined $126.7 million cash on hand as of July 31. The Romney campaign and its affiliated groups reported $185.9 million on hand.