WASHINGTON — His name etched in history as America’s first black president-elect, Barack Obama turned today from the jubilation of victory to the sobering challenge of leading a nation worried about economic crisis, two unfinished wars and global uncertainty.

“The road ahead will be long. Our climb will be steep,” Obama cautioned.

Young and charismatic but with little experience on the national level, Obama smashed through racial barriers and easily defeated Republican John McCain to become the first African-American destined to sit in the Oval Office, America’s 44th president. He was the first Democrat to receive more than 50 percent of the popular vote since Jimmy Carter in 1976.

“It’s been a long time coming, but tonight, because of what we did on this date in this election at this defining moment, change has come to America,” Obama told a victory rally of 125,000 people jammed into Chicago’s Grant Park.

After an improbable journey that started for Obama 21 months ago and drew a record-shattering $700 million to his campaign account alone, Obama scored an Electoral College landslide that redrew America’s political map. He won states that reliably voted Republican in presidential elections, like Indiana and Virginia, which hadn’t supported the Democratic candidate in 44 years. Ohio and Florida, key to President Bush’s twin victories, also went for Obama, as did Pennsylvania, which McCain had deemed crucial for his election hopes.

With most U.S. precincts tallied, the popular vote was 52.3 percent for Obama and 46.4 percent for McCain. But the count in the Electoral College was lopsided — 349 to 147 in Obama’s favor as of early Wednesday, with three states still to be decided. Those were North Carolina, Georgia and Missouri.

With just 76 days until the inauguration, Obama is expected to move quickly to begin assembling a White House staff and selecting Cabinet nominees. Campaign officials said Illinois Rep. Rahm Emanuel was the front-runner to be Obama’s chief of staff. The advisers spoke on a condition of anonymity because the announcement had not yet been made.

With these moves and many others to come upon him quickly, Obama planned a low-key, everyman day-after in his hometown of Chicago. The president-elect was taking his two young daughters to school, and then heading to the gym, with little else on his schedule.

The nation awakened to the new reality at daybreak, a short night after millions witnessed Obama’s election — an event so rare it could not be called a once-in-a-century happening. Prominent black leaders wept unabashedly in public, rejoicing in the elevation of one of their own — at long last.

The Rev. Jesse Jackson, who had made two White House bids himself, said on ABC’s “Good Morning America” that the tears streaming down his face upon Obama’s victory were about his father and grandmother and “those who paved the fights. And then that Barack’s so majestic.”

“He’s going to call on us, I believe, to sacrifice. We all must give up something,” Rep. John Lewis, a Georgia Democrat and leading player in the civil rights movement with Jackson, said on NBC’s “Today” show.

Speaking from Hong Kong, retired Gen. Colin Powell, the black Republican whose endorsement of Obama symbolized the candidate’s bipartisan reach and bolstered him against charges of inexperience, called the senator’s victory “a very very historic occasion.” But he also predicted that Obama would be “a president for all America.”

Bush, whose public approval ratings have plummeted in the waning days of his presidency, was mostly behind the scenes in the last weeks of the historic campaign. He called Obama to congratulate him late Tuesday and scheduled a midmorning statement in the White House Rose Garden.

After the longest and costliest campaign in U.S. history, Obama was propelled to victory by voters dismayed by eight years of Bush’s presidency and deeply anxious about rising unemployment and home foreclosures and a battered stock market that has erased trillions of dollars of savings for Americans.

Six in 10 voters picked the economy as the most important issue facing the nation in an Associated Press exit poll. None of the other top issues — energy, Iraq, terrorism and health care — was selected by more than one in 10. Obama has promised to cut taxes for most Americans, get the United States out of Iraq and expand health care, including mandatory coverage for children.

Obama acknowledged that repairing the economy and dealing with problems at home and overseas will not happen quickly — alluding even in the first blush of victory to the possibility of a second term. “We may not get there in one year or even in one term,” he said. “But, America, I have never been more hopeful than I am tonight that we will get there. I promise you, we as a people will get there.”

Obama faces a staggering list of problems, that he called “the greatest of our lifetime — two wars, a planet in peril, the worst financial crisis in a century.” He spoke of parents who worry about paying their mortgages and medical bills.

“There will be setbacks and false starts,” Obama said. “There are many who won’t agree with every decision or policy I make as president. And we know the government can’t solve every problem.”

The son of a Kenyan father and a white mother from Kansas, the 47-year-old Obama has had a startlingly rapid rise, from lawyer and community organizer to state legislator and U.S. senator, now just four years into his first term. He is the first senator elected to the White House since John F. Kennedy in 1960.

Bush called Obama with congratulations at 11:12 p.m. EST. “I promise to make this a smooth transition,” the president said. “You are about to go on one of the great journeys of life. Congratulations and go enjoy yourself.” He invited Obama and his family to visit the White House soon.