WASHINGTON (CNN) -- Democratic presidential candidate Sen. Barack Obama raised at least $20 million for his presidential campaign during the third quarter of 2007, his campaign announced Monday.
All but about $1 million of those contributions can be used in the primary fight, where the Illinois senator is among the front-running candidates.
In a statement, the Obama camp said the funds were raised from more than 93,000 donors during the quarter, which ended Sunday.
"Many in Washington have spent the last weeks declaring the outcome of this race to be preordained and the primary process a mere formality," said Obama campaign chief David Plouffe, in a veiled reference to Democratic front-runner Sen. Hillary Clinton of New York.
"Yet, in this quarter alone, 93,000 more Americans joined our campaign, because they desire real change and believe Barack Obama is the one candidate who can deliver it," Plouffe said. "This grassroots movement for change will not be deterred by Washington conventional wisdom, because in many ways it is built to challenge it."
Obama's campaign said he has raised at least $74.9 million in primary funds so far this year from 352,000 donors.
Clinton is expected to report between $17 and $20 million in contributions in the third quarter, sources said.
Former North Carolina Sen. John Edwards' campaign announced on a conference call Monday that he raised $7 million during the third quarter.
Edwards, the party's 2004 vice presidential nominee, announced Thursday that he would accept public financing for the primary and general election campaigns and challenged Clinton and Obama to do the same.
Edwards Deputy Campaign Manager Jonathan Prince said the campaign has $12 million cash. Prince said public funding will add $10 million to the campaign's totals.
"We are thrilled with the support we've received from people across the country," Prince said. "Americans from every walk of life are responding to Sen. Edwards' message and bold plans to change Washington."
Edwards has raised more than $30 million so far, and the campaign is on the right track to reaching its goal of $40 million by January, Prince said.
Prince credited the campaign's aggressive grassroots outreach and said Edwards received donations from 150,000 Americans, with 97 percent of the contributions less than $250.
Fundraising is historically slow in the third quarter, which covers the final two months of summer and the first month of fall.
In the second quarter, Obama shattered fundraising records by reporting that he raised $32.5 million, $31 million of which he can use in his bid for the Democratic nomination.
Clinton raised $27 million during this same period and all but $6 million of it can be used in the primary, while Edwards raised more than $9 million in the second quarter.
On Sunday, New Mexico Gov. Bill Richardson reported campaign contributions of $5.2 million for the third quarter, which his campaign said supports his claim that he is a top-tier candidate.
"We continue to count contributions as they are coming in throughout the day, but this figure obviously separates us from the second-tier candidates and makes clear this is a four-person race," Richardson's campaign announced in a prepared statement.
Most political observers put Sens. Clinton, Obama and Edwards as the first-tier candidates for the Democratic nomination.
Though $5.2 million is down from the $7 million reported in the second quarter, the Richardson campaign touted it as "a strong showing in a historically difficult fundraising period."
"Most importantly, this amount ensures we will have the resources we need to compete in the early states like Iowa, New Hampshire, Nevada and South Carolina," it said. "We have strong organizations in those states and continue to expand our field operations by adding staff and opening new offices."
The campaign did not disclose how much it had spent during the quarter or how much cash it had left. Candidates have until October 15 to file a full report with the Federal Election Commission.
On the Republican side, former New York Mayor Rudy Giuliani and former Massachusetts Gov. Mitt Romney are expected to battle again for the top spot. Romney raised nearly $35 million so far this year, with Giuliani $1.5 million behind.
Sources close to the Giuliani campaign say they expect to be atop the pack for the third quarter.
Fred Thompson's numbers will be scrutinized. Thompson raised more than $8 million for his late-starting presidential campaign in the past three months, a Thompson campaign source told CNN on Monday.
Thompson's upcoming Federal Election Commission report will also show 70,000 donors have contributed to the former "Law and Order" star in the third quarter, according to the source, who requested anonymity because the campaign has not yet officially released the information.
Thompson formally entered the presidential race early last month, but he has been raising money since early June. The Tennessee Republican raised close to $3.5 million from approximately 9,000 donors in June, the final month of the second quarter.
Sen. John McCain of Arizona is expected to show he raised more than $5 million this quarter but a McCain adviser said McCain's recent poll numbers in New Hampshire and a busy fundraising schedule next month show that they "have some life."
McCain raised $24.5 million the first two quarters of the year but spent nearly all of the funds raised.
Lower numbers are expected for Sen. Sam Brownback of Kansas, Rep. Duncan Hunter of California, Rep. Ron Paul of Texas, Sen. Tom Tancredo of Colorado and former Arkansas Gov. Mike Huckabee. E-mail to a friend
CNN's Mark Preston, Paul Steinhauser and Lauren Kornreich contributed to this report.