Democratic Sen. Barack Obama has raised $7.2 million for his presidential campaign since the first polls closed on Super Tuesday night, his campaign said Thursday, a remarkable figure that is causing concern among supporters of Sen. Hillary Rodham Clinton.

Meanwhile Thursday, the Clinton campaign asked Obama to debate once a week, but he demurred.

Obama, riding a wave of fundraising from large donors and small Internet contributors, also raised $32 million in January.

Clinton acknowledged Wednesday that she loaned her campaign $5 million late last month as Obama was outraising and outspending her heading into Feb. 5 Super Tuesday contests. Some senior staffers on her campaign also are voluntarily forgoing paychecks as the campaign heads into the next round of contests.

Obama and Clinton outpaced all candidates in 2007, with each raising $100 million.

The Obama campaign said on its Web site that $7.2 million has been received since Tuesday evening. Campaign spokesmen said they were confident the figure was accurate.

Buoyed by strong fundraising and a primary calendar in February that plays to his strengths, Obama plans a campaign blitz through a series of states holding contests this weekend and will compete to win primaries in the Mid-Atlantic next week and Hawaii and Wisconsin the following week.

He campaigned in Louisiana Thursday. The state holds its contest Saturday.

Clinton, with less money to spend and less confident of her prospects in the February contests, will instead concentrate on Ohio and Texas, large states with primaries March 4 and where polling shows her with a significant lead. She even is looking ahead to Pennsylvania's primary April 22, believing a large elderly population there will favor the former first lady.

In a sign of Clinton's increasing concern about Obama's growing strength, her campaign manager, Patti Solis, sent a letter Thursday to the Obama campaign seeking five debates between the two candidates before March 4.

"I'm sure we can find a suitable place to meet on the campaign trail," Solis wrote. "There's too much at stake and the issues facing the country are too grave to deny voters the opportunity to see the candidates up close."

Obama rejected a debate proposed as soon as this Sunday to be broadcast on ABC, but his campaign spokeswoman Jen Psaki said Thursday, "there will definitely be more debates, we just haven't set a schedule yet."