The first quarter financial reports, which were due at midnight Sunday, offer a glimpse into an aspect of the 2008 presidential election that sets it apart. All of the leading candidates have chosen to forgo public campaign financing in order to raise and spend private donations without any limits. Several have raised more than three times as much as any candidate did during the same period before the last election.

The leading Republicans filed their reports Friday and Saturday. Mrs. Clinton and Mr. Obama were the two top fund-raisers in either party. Mrs. Clinton raised $19.1 million for the primary, and $6.9 million for use in the general election (accessible only if she wins the nomination).

Mr. Obama raised $24.8 million for the primary and $1 million for the general election.

The primary campaign of John Edwards, the former senator from North Carolina, said in its filing that he had spent less than $3 million of the $13 million he raised in the quarter, leaving him with $10.7 million in the bank. He raised less than $1 million for the general election.

Campaign finance laws cap contributions to each phase of the race at $2,300, leading to a frantic scramble among the top contenders in each party to assemble networks of fund-raisers, bundlers, who can collect $2,300 checks from friends and associates. But dependence on such large checks can pose a risk to campaign momentum because the big donors cannot continue to give as the campaign continues.

Although Mr. Obama has sought to publicize his campaign’s emphasis on small contributions, he, too, depended heavily on a relatively small number of big checks. About 4,800 supporters gave the maximum $2,300 to his primary campaign, accounting for about $11 million, nearly half his total. About 75 of those donors gave another $2,300 to his general election fund, according to an analysis of his campaign’s filing.

On Sunday, his campaign released a list of about 130 bundlers who had each raised $50,000, for more than $6.5 million, about a quarter of his total for both races.

Mrs. Clinton, though, depended even more heavily on a relatively narrow base of wealthy and committed donors who contributed about $19 million. More than 5,100 gave about the legal limit of $2,300 to her primary campaign, contributing more than $11.7 million, nearly two thirds of her primary fund. What is more, nearly 3,000 of those who had already hit the $2,300 limit for the primary also contributed $2,300 toward her general election fund.