Washington - Barack Hussein Obama will complete a remarkable breakthrough when he is sworn into office on Tuesday.
As the first African-American president, he will immediately, and forever, stand apart from the 42 white men who preceded him. But his significance goes beyond that indelible achievement.
Obama will also become America's first global president, taking charge under the shadow of what he calls "the worst recession since the Great Depression," a worldwide contagion with no end in sight.
His rise to power resembles John F. Kennedy's triumph over religious prejudice, though it is an even more profound one, because of America's long, defining struggle over race. Like JFK, he embodies generational change and has triggered a level of anticipation that exceeds anything in recent memory.
In a sense, Obama will be an entirely new kind of president: a political figure and an international cultural phenomenon.
His most basic political theme - a simple message of hope - has found a receptive audience across borders.
"He's telling the whole world it doesn't matter if you grew up poor or had dark skin. You can be a world leader," said presidential historian Douglas Brinkley of Rice University. That idea resonates not only in the United States but also in "Kenya or Indonesia [and] Pakistan and Colombia and beyond."
In Kennedy's time, a young American president and his glamorous wife seized the imagination of foreign audiences. But the world they charmed was, in some ways, rather primitive by comparison with today's.
The revolutionary web of online networks that Obama exploited in winning the White House has made Washington the epicenter of a planet drawn closer together than ever before. The French foreign minister, Bernard Kouchner, observed that Americans had held a "world election" in 2008, and interest in Obama continues to run high in other countries.
Thanks to modern communications and his personal appeal, Obama's inaugural address could well draw a larger audience than any other speech ever delivered.
"It's only natural, since America is the world's media center, that we'd eventually have a leader that is playing to an international audience," said Brinkley.
Like many others his own age and younger, the 47-year-old Obama grew up in an era in which globalization is taken for granted. His personal life and perspective were shaped by his African roots and Indonesian childhood, both of which may have implications for his presidency.
As a candidate, he argued that, because his step-grandmother lives in a hut in Kenya and his half-Indonesian sister is married to a Chinese-Canadian, his arrival in the White House would, by itself, help transform the country's image overseas.
He and his choice for secretary of state, Hillary Clinton, have promised to put a new face on American diplomacy and reach out to Iran, Syria and other adversaries. Drawing a bead on one of the greatest irritants in U.S. relations with foreign leaders, Obama plans to swiftly redeem his promise to close the military prison at Guantanamo Bay in Cuba.
"We will send a message to the world," he said, "that we are serious about our values."
Even skeptics, convinced that expectations are too high for Obama to meet, think that a new cast of leaders in Washington will give U.S. foreign policy a fresh start.
"The music's going to change. The process is going to change. The faces attached to American diplomacy will change. And people in other countries are going to be falling all over one another to give us the benefit of the doubt," said Aaron David Miller, a former State Department adviser now at the Woodrow Wilson Center. "The fact that Barack Obama knows the world is a complicated place, that he can be empathetic and has a sense of nuance and context, is all very important."
The way he is taking office, becoming the world's most powerful figure through democratic means, also sends a powerful message about American values. It has inspired a legion of admirers, many of them young, from the inner-city to Tobacco Road in the Carolinas to the remote reaches of the Far East.
News of his election was cheered in the Jakarta elementary school he once attended, the Kenyan village where his relatives live and in countless cafes on every continent.
A 16-year-old girl in a provincial Chinese city more than a thousand miles from Beijing excitedly e-mailed an American friend: "We like his energy, enthusiasm, youth and his speech! We watched his speech when he won the presidential election, it's moving and encouraging!"
But as he takes office, Obama will be grappling with the worst economy to confront a new president since Franklin D. Roosevelt was sworn in 75 years ago.
Because of the global financial meltdown, Obama has "an unprecedented opportunity to do things you ordinarily can't do and change the political landscape," said Benjamin Ginsberg, a Johns Hopkins political scientist. He can initiate federal programs and regulatory reforms that attract millions of new voters to the Democratic Party, as Roosevelt did with his New Deal, he said.
Back in the 1930s, America was only beginning to assert global military and economic authority, and Obama won't have the luxury of isolating the U.S. economy. What happens on Wall Street and in Washington reverberates around the world overnight, as last year's financial crisis demonstrated.
The war in Gaza is a tragic reminder that unforeseen and uncontrollable events can wreck the best-planned agendas.
"Unfortunately, international things tend to intrude, sometimes with big explosions and unpleasant results," said Ginsberg. Obama "will try to hold off our foreign foes while he fixes the domestic economy."
The inauguration of a new president, by definition, brings change. But not every handover of power becomes a landmark.
Obama's signals the rise of a new generation - particularly those Americans under 30 who voted for him by better than 2-1 and reflect the country's increasing diversity, as symbolized by its first biracial president.
In a similar way, Kennedy's presidency, near the height of the Cold War with the Soviet Union, represented the passing of a torch to the generation that came of age in World War II.
Ronald Reagan, in 1981, brought sweeping tax and spending changes to Washington and began an era of conservative dominance in the country that may now be coming to a close.
But it was Franklin Roosevelt, in 1933, who may offer the closest parallel.
FDR seems to be weighing on Obama's mind these days, despite his near-obsession with Abraham Lincoln, as reflected by his decision to retrace the 16th president's rail route yesterday from Philadelphia to Washington, by way of Baltimore.
Roosevelt, under the system then in place, did not take office until March. The Great Depression was already under way, but FDR kept his distance from incumbent President Herbert Hoover during the three-month transition period after the election. He did not want to be associated with the policies that helped bring the nation to its knees.
This winter, with the country again at a crossroads, Obama has taken the opposite approach. He has conducted perhaps the most active transition in history, enjoying full cooperation from President George W. Bush.
Afraid of further deterioration before he took charge, the president-elect and his aides began negotiating with Congress over the shape of an economic stimulus package that will be a centerpiece of his first-year agenda.
He also hasn't waited for Inauguration Day to begin shaping public opinion. To sell his plan, he made a campaign-style stop at an Ohio wind-turbine factory on Friday and, earlier this month, delivered what some saw as a State of the Union-like address.
In a sober look at the world he soon will officially inherit, Obama warned Congress that every day that it delayed, more people would lose their jobs, and he told the public that things will likely get worse before they get better.
In an apparent nod to JFK, he said that Americans should ask not " 'what's good for me?' but 'what's good for the country my children will inherit?' " And borrowing FDR's famous phrase, he ended on an upbeat note. Obama invoked the can-do spirit of past generations, which, he said, had managed to successfully overcome challenges posed by "war and depression and fear itself."