President Obama and the Democrats shattered the election cycle’s fund-raising record with a $181 million haul for September, the campaign announced on Saturday morning.

The amount — a mix of funds raised directly by the campaign and large checks taken in by the Democratic National Committee — was even more than some earlier reports had suggested. And while it did not quite match the roughly $191 million Mr. Obama and the Democrats raised during the same month four years ago, the announcement offered a jolt of good news for Mr. Obama’s supporters in the wake of a lackluster debate performance on Wednesday that left many of them worried.

The campaign began e-mailing supporters early Saturday morning and announced the news on Twitter shortly after 10 am.

An e-mail from Mr. Obama’s campaign manager, Jim Messina, with the subject line “This is big, big news,” included testimonials from donors who had contributed. “The people and the stories behind these numbers are what make this grass-roots organization so powerful,” Mr. Messina wrote.

Mitt Romney has not yet announced his fund-raising totals for the month. But a Romney spokeswoman said that the Republicans had done well after Wednesday’s debate, raising $12 million online in less than 48 hours, more than in the wake of Mr. Romney’s selection of Representative Paul Ryan as his running mate. Sixty percent of the money came from first-time donors, according to the campaign.

September is often a strong month for presidential campaign fund-raising, as voters begin to focus on the race and candidates’ hard-core supporters begin ramping up for the general election. Mr. Obama’s September fund-raising included money contributed during the Democratic convention in Charlotte, N.C., when the president, his wife, Michelle, and former President Bill Clinton all delivered major speeches.

The president and his party had received donations from close to four million people since Mr. Obama announced his re-election bid last year, the campaign said. September’s totals included contributions from 1,825,813 people, 567,000 of them new donors, the campaign said.

The September totals mark a second strong fund-raising month in a row for Mr. Obama, at a time when his campaign is bracing for an onslaught of late advertising from Republican-aligned “super PAC’s” and other outside groups. In August, Mr. Obama and the Democratic committee raised $114 million, more than the $111.6 million raised by Mr. Romney and the Republicans.

Mr. Obama did not announce how much cash his campaign had on hand going into October, and his campaign does not have to file detailed disclosures with the Federal Election Commission until later this month. But he is likely to show strong donations from small donors relative to Mr. Romney, a difference that gave Mr. Obama a critical advantage in cash flow over Mr. Romney in August, when the Republican candidate borrowed $20 million to get through the summer.

While Mr. Obama has raised more than half of his total cash on donations of under $200, Mr. Romney has relied far more on large donors giving the maximum check to the candidate and his party. Without a large stream of grass-roots money, Mr. Romney has had to spend more time fund-raising in recent months than his campaign would like, leaving less time to meet voters in swing states.