“The flip side of this — and I want to make sure this is also clear — we also believe that it is paramount to begin doing everything we said we would do in the campaign,” Mr. Gibbs said. “We know expectations are high. But disappointment if we didn’t try to do the things that we said we were going to do would be far, far greater than anything else. People went to the polls and elected Barack Obama because they believed the fact not only that he could do what he said, but that he would try to do what he said.”

The challenge facing Mr. Obama today is similar to one that faced Bill Clinton in 1992, the last time a president arrived in Washington with anything approaching the level of excitement Mr. Obama’s election set off around the country.

As Election Day approached in 1992, it was apparent from the crowds that Mr. Clinton drew, in their size and their faces, that his supporters expected big things after a campaign in which Mr. Clinton had promised a dramatic revamping in health care coverage and programs for the poor. At the time, a senior adviser who was traveling with him, Paul Begala, warned Mr. Clinton to add some caveats to his speeches, to avoid voter letdown should it take time to accomplish things as president.

“I remember talking about this to him in the closing days of the campaign,” Mr. Begala said. “And he started saying, ‘We didn’t get into this overnight and we’re not going to get out of it overnight.’ ”

“So I remember him talking about it and doing it — and it didn’t have any effect on the citizens,” Mr. Begala said. That was one reason, he said, that Democrats lost control of Congress two years later.

A nearly 500-point drop in the Dow Jones Industrial Average on Wednesday was a reminder that Mr. Obama’s election did not bring the financial crisis to a close, and that the economic downturn could limit his ability to pursue his full agenda right off the bat by demanding an immediate focus on trying to pull the nation out of recession. And, even if Americans are ready to bear with Mr. Obama as he pursues policy proposals, they may not as readily accept the sort of compromise that legislative accomplishment often requires.