The New York lawmaker, a potential 2008 presidential candidate, raised more than $6 million in the first three months of the year, according to papers filed Thursday with the Federal Election Commission.
The $2 million-a-month fundraising pace gave her $19.7 million cash on hand at the end of March for her Senate re-election.
"It's mind-blowing. She is raising money at a presidential level," said Doug Muzzio, a professor at Baruch College in New York.
The two main challengers to Clinton's bid for a second term each reported less than $500,000 as they vie for the Republican nomination.
Former Yonkers mayor John Spencer raised $1.1 million during the first quarter of this year and had $340,000 on hand, while Kathleen Troia "KT" McFarland, a former Reagan-era Pentagon official, raised about $200,000 and has $430,000 on hand.
The Clinton campaign trumpeted how much of its money came from the small-level, Internet-driven donations. More than 250,000 individuals donated to her 2006 campaign, and only one out of every 20 donations she received this quarter were larger than $100, the campaign said.
The campaign also spent a small fortune to raise funds — $3.4 million in three months.
Muzzio argued those expenditures show she is planting the seeds for the sort of national political operation needed to run for president.
"A quarter of a million donors are really a quarter of a million future activists. They are developing an infrastructure of people and a database that rivals Bush's database in 2004," he said.
Campaign spokeswoman Ann Lewis said the increase in expenses is typical of a campaign that is still signing up new donors.
The junior senator from New York also travels the country regularly, raising cash for herself and other Democratic candidates, though she insists she isn't thinking beyond the 2006 race.
Plenty of her supporters are.
"I didn't give her money for the Senate, I want her to run for the White House," said $201 Clinton donor Martin Rogoff.
A Philadelphia-area businessman, Rogoff said he doubts other contributors think she needs money for a so far lopsided Senate contest.
"I don't believe anybody donating believes this is for the Senate. I think it's time we had a woman in the White House," he said.
Other Senate campaign totals available Thursday suggest Clinton is in a league of her own.
In the closely watched Pennsylvania race, Democrat Bob Casey reported raising $2.2 million in the first three months of the year, bringing his available cash to $4.5 million. Incumbent Sen. Rick Santorum, a Republican, did not release his campaign figures Thursday.
Sen. Debbie Stabenow, D-Mich., raised $1 million and ended the quarter with $6.3 million on hand.
In New Jersey, Democratic Sen. Robert Menendez raised $2.5 million for his 2006 campaign in the first three months of the year, while Republican challenger Tom Kean Jr. raised about $1.6 million.
Menendez has $6.36 million on hand, compared to about $2 million for Kean.
Massachusetts Sen. John Kerry's political action committee raised $1.1 million, giving more than 60 percent to Democratic congressional candidates. Kerry was his party's 2004 nominee for president and is considered a potential 2008 candidate.