WASHINGTON — Rebounding from weak fundraising in January, Senator Clinton is expected to raise $35 million in February, a figure Senator Obama’s campaign said it would surpass.

The $35 million would be Mrs. Clinton’s biggest fundraising mark yet and represents a remarkable recovery for her campaign.

Mr. Obama’s campaign reacted promptly, promising an even higher number, but divulging no totals.

“We’ve raised considerably more than that,” an Obama spokesman, Bill Burton, said.

Mr. Obama told reporters on his campaign plane, “I have no idea how much money we’ve raised, but we’ve been paying our bills. Right now, I believe we’re doing very good.”

That would make February an astounding fundraising month for the Democrats. At that rate, both candidates would break records for contestants in a primary fight.

Mrs. Clinton has been struggling to recover from weak fundraising in January. She raised nearly $14 million in January to Mr. Obama’s $36 million.

Clinton officials, including the campaign chairman, Terry McAuliffe, announced the totals in a conference call with contributors. The campaign announced that it had raised the money from 300,000 donors, including 200,000 new contributors, most of them donating through the Internet. Aides said almost all the money was for the primary election.

Despite her increased fundraising, Mr. Obama is still outspending her in the crucial March 4 primary states of Ohio and Texas. As of Tuesday, Mr. Obama had spent a total of $7.5 million in advertising in the two states. Mrs. Clinton had spent $4.6 million.

Mr. Obama also was getting help from labor unions. The Service Employees International Union began spending $1.4 million in ads in support of Mr. Obama in Ohio and Texas. The United Food and Commercial Workers International Union was spending nearly $200,000 in ads in Ohio.