WASHINGTON — A Democratic presidential candidate, Senator Obama, raised $32 million in the single month of January, a whopping figure that has permitted the campaign to boost staff and extend advertising to states beyond the sweeping February 5 contests, aides said today.

Mr. Obama is now advertising in 20 of the 22 states in play for next week’s Super Tuesday and plans to begin advertising in seven more states that hold primaries or caucuses later in February. Senator Clinton is advertising in 12 Super Tuesday states, including her own home state of New York.

With John Edwards out of the race, Mrs. Clinton and Mr. Obama are in a fierce race for delegates to secure the nomination. February 5 offers the biggest single opportunity for delegates, but is impossible for either one to seal the nomination on that day.

An Obama campaign manager, David Plouffe, said the campaign attracted 170,000 new donors for a total of 650,000 donors overall. The $32 million raised in one month matches the campaign’s best three-month fundraising period in 2007, when the campaign raised $30 million in primary money and $2 million for the general. The money raised in January was all for the primaries.

“We think that the strength of our financial position and the number of donors does speak to financial sustainability if it ends up going through March and April,” Mr. Plouffe said of the race. “We think we will have the financial resources to conduct vigorous campaigns in the states to come.”

Mr. Plouffe said the campaign, surprisingly, had its best single fundraising period the day after losing the New Hampshire primary to Mrs. Clinton. In January, Mr. Obama won the Iowa caucuses and the South Carolina primary; Mrs. Clinton won the New Hampshire primary and the Nevada caucuses. She also won popular votes in Michigan and Florida where the candidates did not campaign because no nominating delegates were at stake.