Obama raised $36.1 million in January -- the second-biggest month for a presidential candidate, according to the Federal Election Commission. Democratic Sen. John F. Kerry had a $40-million month in May 2004.
Hillary Rodham Clinton's financial situation, the onetime Democratic front-runner reported $2.5 million in unpaid bills as of Jan. 31. She lent her campaign $5 million in January. According to her filing, she would pay herself 1.26% interest if she collected on the debt by tapping her donors.
McCain also used loans to remain in contention, drawing $950,000 from a line of credit last month. But the Arizona senator's fortunes changed Jan. 8, the day he won the New Hampshire primary.
Between then and Jan. 31, McCain raised $9.3 million of the $11.7 million he received from individual donors and political committees last month.
"His ability to raise money increases geometrically as donors try to board the train," said Republican strategist Jim Brulte, a McCain backer. "You don't have to pay the fare to hop on the bandwagon. But most people do, as a matter of courtesy."
McCain vastly out-raised Republican rival Mike Huckabee. The former Arkansas governor collected $4 million in January after winning the Iowa caucuses -- by far his biggest fundraising month. He raised $9 million in all of 2007.
McCain, an advocate of campaign finance restrictions, considered accepting federal matching funds for the primary last year when his campaign was floundering. That changed with his string of victories. By foregoing the taxpayer money, McCain can raise and spend millions more between now and the GOP convention.
But he also has jousted with Obama over whether the Illinois senator would accept federal money in the general election if each gained his party's nomination. By accepting the federal money, a candidate agrees to operate under caps that limit spending in the general election to about $85 million. The funds come from a presidential financing program paid for with a $3 checkoff on tax returns.
Obama had said he would consider operating within the federal restrictions if his opponent agreed to do so. Given his vast fundraising advantage in the primaries, it seems less likely that he would want to abide by the restrictions.
The bulk of Obama's money comes from high-end donors. But of the $36.1 million he raised last month, nearly a third -- $11.9 million -- came in donations of $200 or less.
He has the largest network of donors -- nearly 1 million people -- of any presidential candidate. Because the smaller donors have not reached the federal campaign contribution limit of $2,300 per person, Obama can go back to them for more money.
Clinton, by contrast, raised $3.4 million of her $13.9 million in increments of $200 or less in January. Her campaign's fundraising is said to be moving at a faster clip in February.
Despite struggling to gather votes and delegates, Rep. Ron Paul (R- Texas) continued raising significant money in January -- $4.4 million -- pushing his total to nearly $40 million, his filing showed.
McCain's latest loans, drawn in increments of $475,000 on Jan. 2 and Jan. 7, push the total that he has borrowed to nearly $4 million since November. McCain is paying 8.5% interest on the loan from Fidelity & Trust Bank of Maryland.
McCain's debt pales compared with that of onetime rival Mitt Romney, who lent himself $7 million in January, pushing his total commitment to $42.3 million. Romney spent $98 million of his own and donor money as of the end of January, then dropped out and endorsed McCain this month.
Like Romney, onetime GOP front-runner Rudolph W. Giuliani proved that money doesn't always win elections. He raised $64.7 million for his failed presidential bid. He also ended January with $9 million left over -- surprising some experts given that Giuliani's entire campaign revolved around winning in Florida on Jan. 31.
"Could he have won Florida with that $9 million?" asked Anne Dunsmore, who had been Giuliani's chief fundraiser until the summer. She noted that Giuliani might have bills that won't come due until later.
"It is a horrible PR error, but it was probably a ridiculously prudent decision," Dunsmore said. Giuliani's accountants appear to have been "running the exit strategy," she said.
Times researcher Maloy Moore and data analyst Sandra Poindexter contributed to this report.