While Roosevelt refused to get involved in prescribing economic medicine between his election in 1932 and his inauguration, advisers said Mr. Obama had concluded that he could not follow that example and remain silent until he was sworn in. At the same time, they said, Mr. Obama understands he should not overstep his bounds and wants his inauguration to mark a clean break from the past.

“Those who say wait and let the process unfold for two months before the inauguration are sorely mistaken,” said Jack Quinn, a former top official in the Clinton administration. “We are in such turmoil that his clearly and firmly putting his hand on the tiller is absolutely critical. He needs to do this. He needs to be in the middle of this.”

Mr. Obama has been conferring with Congressional leaders about a possible package of $100 billion for public works, unemployment benefits, winter heating assistance, food stamps and aid to cities and states that could be passed during a lame-duck session the week of Nov. 17. He has also been talking regularly with Treasury Secretary Henry M. Paulson Jr. about the economic environment and hopes to work closely with him during this interim period as Mr. Paulson makes decisions about how to invest the $700 billion given him by Congress to shore up the financial system.

But there are limits to Mr. Obama’s capacity to act in the short term. The politics of assembling a stimulus package in this netherworld between administrations could be difficult to overcome as he tries to balance pent-up demand from now-victorious Democrats eager to use their power of the purse with the reality that Mr. Bush still holds the veto pen for 77 more days. In the end, Democrats said, Mr. Obama and Congressional leaders would pare their spending plans if they could not get Mr. Bush and Senate Republicans to agree, then come back in January when they have unfettered control.

“If he gets out there too much and gets too enmeshed in policy disputes before he’s inaugurated, when he doesn’t have control of the federal bureaucracy, that could really backfire on him,” said Elaine C. Kamarck, who was Vice President Al Gore’s domestic policy adviser in the 1990s. “It’s a really delicate balance he has to strike.”

Whatever collaboration there may be in the short term, Mr. Obama represents the end of the Bush era in the long term. Yet he will find himself dealing with the Bush legacy for years to come. He promised on the campaign trail to close the detention facility at the United States naval base at Guantánamo Bay, Cuba, but analysts in both parties expect that to be more difficult than he imagines. He will inherit a deficit that could approach $1 trillion next year, which could curtail his ambitions, like expanding health care coverage.