WASHINGTON (AP) — Barack Obama swept to victory as the nation’s first black president Tuesday night in an electoral college landslide that overcame racial barriers as old as America itself. “Change has come,” he told a jubilant hometown Chicago crowd estimated at nearly a quarter-million people.

The son of a black father from Kenya and a white mother from Kansas, the Democratic senator from Illinois sealed his historic triumph by defeating Republican Sen. John McCain in a string of wins in hard-fought battleground states — Ohio, Florida, Iowa and more. He captured Virginia and Indiana, too, the first candidate of his party in 44 years to win either.

Obama’s election capped a meteoric rise — from mere state senator to president-elect in four years.

Spontaneous celebrations erupted from Atlanta to New York and Philadelphia as word of Obama’s victory spread. A big crowd filled Pennsylvania Avenue in front of the White House.

In his first speech as victor, to an enormous throng at Grant Park in Chicago, Obama catalogued the challenges ahead. “The greatest of a lifetime,” he said, “two wars, a planet in peril, the worst financial crisis in a century.”

He added, “There are many who won’t agree with every decision or policy I make as president, and we know that government can’t solve every problem. But I will always be honest with you about the challenges we face.”

McCain called his former rival to concede defeat — and the end of his own 10-year quest for the White House. “The American people have spoken, and spoken clearly,” McCain told disappointed supporters in Arizona.

President Bush added his congratulations from the White House, where his tenure runs out on Jan. 20. “May God bless whoever wins tonight,” he had told dinner guests earlier.

Obama, in his speech, invoked the words of Lincoln, recalled Martin Luther King Jr., and seemed to echo John F. Kennedy.

“So let us summon a new spirit of patriotism, of service and responsibility where each of us resolves to pitch in and work harder,” he said.

He and his running mate, Sen. Joseph Biden of Delaware, will take their oaths of office as president and vice president on Jan. 20, 2009. McCain remains in the Senate.

Sarah Palin, McCain’s running mate, returns to Alaska as governor after a tumultuous debut on the national stage.

He will move into the Oval Office as leader of a country that is almost certainly in recession, and fighting two long wars, one in Iraq, the other in Afghanistan.

The popular vote was close — 51.7 percent to 47 percent with 84 percent of all U.S. precincts tallied — but not the count in the Electoral College, where it mattered most.

There, Obama’s audacious decision to contest McCain in states that hadn’t gone Democratic in years paid rich dividends.

Shortly after 2 a.m. the East, The Associated Press count showed Obama with 349 electoral votes, well over the 270 needed for victory. McCain had 144 after winning states that comprised the normal Republican base, including Texas and most of the South.

Interviews with voters suggested that almost six in 10 women were backing Obama nationwide, while men leaned his way by a narrow margin. Just over half of whites supported McCain, giving him a slim advantage in a group that Bush carried overwhelmingly in 2004.

The results of the AP survey were based on a preliminary partial sample of nearly 10,000 voters in Election Day polls and in telephone interviews over the past week for early voters. Obama has said his first order of presidential business will be to tackle the economy. He has also pledged to withdraw most U.S. combat troops from Iraq within 16 months.

In Washington, the Democratic leaders of Congress celebrated.

“It is not a mandate for a party or ideology but a mandate for change,” said Senate Majority leader Harry Reid of Nevada.

Said Speaker Nancy Pelosi of California: “Tonight the American people have called for a new direction. They have called for change in America.”

Democrats also acclaimed Senate successes by former Gov. Mark Warner in Virginia, Rep. Tom Udall in New Mexico and Rep. Mark Udall in Colorado. All won seats left open by Republican retirements.

In New Hampshire, former Gov. Jeanne Shaheen defeated Republican Sen. John Sununu in a rematch of their 2002 race, and Sen. Elizabeth Dole fell to Democrat Kay Hagan in North Carolina.

Biden won a new term in Delaware, a seat he will resign before he is sworn in as vice president.

The Senate’s Republican leader, Mitch McConnell, survived a scare in Kentucky, and in Georgia Sen. Saxby Chambliss hoped to avoid a December runoff.

The Democrats piled up gains in the House, as well.

They defeated seven Republican incumbents, including 22-year veteran Chris Shays in Connecticut, and picked up nine more seats where GOP lawmakers had retired.

At least three Democrats lost their seats, including Florida Rep. Tim Mahoney, turned out of office after admitting to two extramarital affairs while serving his first term in Florida. In Louisiana, Democratic Rep. Don Cazayoux lost the seat he had won in a special election six months ago.

The resurgent Democrats also elected a governor in one of the nation’s traditional bellwether states when Missouri Attorney General Jay Nixon won his race.

An estimated 187 million voters were registered, and in an indication of interest in the battle for the White House, 40 million or so had already voted as Election Day dawned.

Obama sought election as one of the youngest presidents, and one of the least experienced in national political affairs.

That wasn’t what set the Illinois senator apart, though — neither from his rivals nor from the other men who had served as president since the nation’s founding more than two centuries ago. A black man, he confronted a previously unbreakable barrier as he campaigned on twin themes of change and hope in uncertain times.

McCain, a prisoner of war during Vietnam, a generation older than his rival at 72, was making his second try for the White House, following his defeat in the battle for the GOP nomination in 2000.

A conservative, he stressed his maverick’s streak. And although a Republican, he did what he could to separate himself from an unpopular president.

For the most part, the two presidential candidates and their running mates, Biden and Republican Gov. Sarah Palin of Alaska, spent weeks campaigning in states that went for Bush four years ago.

McCain and Obama each won contested nominations — the Democrat outdistancing former first lady Hillary Rodham Clinton — and promptly set out to claim the mantle of change.

Obama won California, Colorado, Connecticut, Delaware, the District of Columbia, Florida, Hawaii, Illinois, Indiana, Iowa, Maine, Maryland, Massachusetts, Michigan, Minnesota, Nevada, New Hampshire, New Jersey, New Mexico, New York, Ohio, Oregon, Pennsylvania, Rhode Island, Virginia, Vermont, Washington and Wisconsin.

McCain had Alabama, Alaska, Arizona, Arkansas, Idaho, Kansas, Kentucky, Louisiana, Mississippi, Nebraska, North Dakota, Oklahoma, South Carolina, South Dakota, Tennessee, Texas, Utah, West Virginia and Wyoming.

He also won at least four of Nebraska’s five electoral votes, with the other one in doubt.