For more than a year, Barack Obama ran as the man from hope — or at least a man of hope. The implicit notion was that Americans could feel free to hope again, that they could dare to believe, and that the very act of hoping could be redemptive, and effective, too. Obama has been in office for little more than a month, and it is clear that hope is the thing with feathers. It flew away.

Until last week. Hope is back, or at least it is back in the Obama repertoire.

The president is a luminous figure, a symbol of American possibility, the personification of decades of dreams, particularly for black Americans. (So was John F. Kennedy to Catholics, and Ronald Reagan to conservatives.) But for almost a month’s time the world’s most hopeful character had become one of the world’s biggest downers.

Let’s leave aside this morning any qualms we might have about a man who can pick up and then put down the hope handle with such apparent ease. Instead let’s examine the tension between optimism and pragmatism, and the difficult equilibrium between rallying the country for a challenge and providing it with a sobering view of that challenge.

The president’s nationally televised speech was something of a wedding reception. Something borrowed: His address subtly embedded phrases from two men who held the same seat in the Senate, Daniel Webster (“something worthy to be remembered”) and Kennedy (“twilight struggle”). Something blue: He issued a clear warning of the dangers ahead.

But he combined all of that with a clarion call for action and an assurance — this you might think of as Reaganesque — that Americans could pull out of the current crisis and pull off something remarkable, like providing health care to all Americans. It’s hard enough to do that rhetorically. It will be doubly difficult to do it realistically.

Yet the last week marked a significant passage in the current crisis. Americans have known for some time that the economy was in turmoil, and they have seen their neighbors if not themselves lose jobs, savings, confidence and, yes, hope. But last week the crisis seemed to have been transformed from something transitory to something stubbornly resistant to reasonable and customary remedy.

That’s why the Obama address in the House chamber Tuesday was so important — one of those moments, like Franklin Roosevelt’s speech after Pearl Harbor or Lyndon Johnson’s speech after the Kennedy assassination, when the nation welcomed a big speech in a big venue about a big topic. Never mind that the Obama speech had strains of his Iowa caucus victory remarks and his acceptance speech at the Denver convention. The president had the nation’s attention, and with his speech he scratched on the wall of history.

For all the talk of the president’s Lincoln obsession — one cannot fault the man’s taste, though perhaps his hubris — this was a speech that seemed deliberately to use FDR as its model. The president pointedly used the word “rebuild,” but in truth the blueprint he set out last week was not only to rebuild the country, but also to build a different country.

Roosevelt’s task, too, was to rebuild a country racked by Depression and hobbled with hopelessness. (Obama’s challenge, right now at least, is not quite as great.) But Roosevelt used the crisis to construct a different kind of country entirely, one where the federal government no longer intruded on the ordinary citizen’s life only when he went to the post office (the model used by the three Republican presidents who preceded FDR) but instead played an activist role in stimulating the economy and perhaps actually running the economy, or at least some sectors of it.

The irony is that some of the modern equivalent of FDR’s New Deal began under perhaps the most devoutly conservative president since William McKinley; it was George W. Bush’s administration, after all, that put Washington in such a commanding position over the nation’s banks. But Obama, deftly building on the idea that an economic crisis is a political opportunity, clearly wants the country that emerges from the current upheaval to be a different country, with substantially different financial, health and educational infrastructures.

Last week’s speech was the functional equivalent of a State of the Union address, though Obama technically won’t give one of those for another 10 months. But State of the Union addresses generally are dreary affairs, important sounding but not really significant, long laundry lists of programs and proposals that everyone knows are going nowhere. Not so the Obama address.

The Republicans are diminished and in disarray — don’t let their near unanimity on the stimulus fool you — and polls show that the country clearly wants its young president to succeed. The public is giving him a break. But it is also giving him more leeway than any president of our time.

We don’t yet know what Obama’s America will look like, just as no one, not even Roosevelt, knew in March 1933 what New Deal America would look like when the president was finished. But if the current president has his way, the country will not look like the America of February 2009. That is the real meaning of last week.

“Last week marked an end to three years of a nation’s drifting from bad to worse, an end to helpless acceptance of a malign fate,” said the editorial page of The Wall Street Journal after FDR took power. “For an explanation of the incredible change which has come over the face of things here in the United States in a single week we must look to the fact that the new administration in Washington has superbly risen to the occasion.”

Neither of those sentences quite applies to Obama’s Washington, not quite yet, and it surely won’t be the Journal’s inclination to salute Obama quite that way anytime soon. Though Roosevelt didn’t precisely know where he was leading the country, it was clear in the winter of 1933 that he was at the very least leading it somewhere. Three quarters of a century later, Americans have reason to feel the same way.