Barack Obama staged his arrival in Washington to evoke Abraham Lincoln's, but the historical echo is faint. Lincoln's famous train ride to his 1861 inauguration traversed a landscape of bitterness and strife. He had to speed through Baltimore "like a thief in the night" for fear of riots and possible assassination. Obama, by contrast, was met by tens of thousands of Baltimoreans who braved subfreezing temperatures to cheer the new president. As Obama made his way to the capital, he crossed a landscape of hope.

Rarely has a new presidency been greeted with such a consensus of goodwill — and rarely has a new president so needed it.

The importance of Obama's historical breakthrough can hardly be overstated. Slavery vexed the Founding Fathers; if not for Lincoln's iron determination, it would have ripped the nation apart. For nearly a century after African-Americans were freed from bondage, American society still relegated us to a corner reserved for second-class citizens. Having a black man as president does not magically eliminate racial disparities in income or wealth; it does not fix inner-city schools, repair crumbling neighborhoods or heal dysfunctional families. Psychologically, though, it changes everything.

Our mental furniture is being rearranged. The advent of Obama's presidency brings the African-American experience to center stage, but does so in a way that allows society to congratulate itself on having come so far. The implications for black Americans are even more profound. Seeing Obama in the White House obliterates any logic behind self-imposed limits on imagination and ambition.

These are huge impacts — so it's ironic that, in the end, race is likely to be secondary in defining Obama's place in history.

Since Obama's election, I've heard more than one friend joke sardonically that the nation has said sure, a black man can run the country, go right ahead and take your turn — now that the economy is in the tubes, the financial system is a wreck, we're mired in two wars, global warming is parboiling the planet, the government has been forced to spend a trillion dollars or more just to stave off utter ruin and there's precious little money left to finance desperately needed reforms in healthcare, education, energy, infrastructure ...

Expectations that Obama will be able to solve this daunting array of problems are strikingly high. A new Washington Post poll finds that 61 percent of Americans have a "good amount" or "great deal" of confidence that Obama will make the right decisions for the country. A remarkable 72 percent are "fairly" or "very" confident that Obama's economic program — whatever it ultimately turns out to be — will improve the economy.

An Associated Press poll reports that 65 percent of Americans believe Obama will be an "above average" president, including 28 percent who expect him to be "outstanding."

Conventional wisdom is that Obama risks losing public support through disillusionment as people discover that he can't wave a magic wand and make everything better.

But the conventional wisdom has been wrong about Obama so many times over the past year.

The truth is that no one knows whether Barack Obama will be a good president, much less a great president. All that anyone, including Obama, can be sure of is that his will be a consequential presidency — an important piece of knowledge. It took the Sept. 11, 2001, attacks to broaden the scope and ambition of George W. Bush's presidency, for better or worse. Obama takes office knowing beyond all doubt that he has no choice but to swing for the fences.

Two years ago, as Obama was launching his campaign — over the objections of the Democratic Party establishment, which was still listening to the conventional wisdom — I interviewed him in his Senate office. I was struck by his confidence and his conviction that this was his time, and especially by how unflappable he appeared to be. I saw him last week, after a campaign that had us on the edge of our seats for months, and he seemed temperamentally unchanged.

Our new president is a man who knows exactly who he is. The nation, filled with hope, is about to find out.

Eugene Robinson part of The Washington Post Writers Group. Reach him at eugenerobinson@washpost.com.