WASHINGTON (AP): Barack Obama effectively clinched the Democratic presidential nomination Tuesday after a grueling marathon, based on an Associated Press tally of convention delegates, becoming the first black candidate ever to lead a major U.S. party in a run for the White House.

Campaigning on an insistent call for change, Obama outlasted former first lady Hillary Rodham Clinton in a historic race that sparked record turnout in primary after primary, yet exposed deep racial and gender divisions within the party.

The tally was based on public declarations from delegates as well as from another 15 who have confirmed their intentions to the AP. It also included 11 delegates Obama was guaranteed as long as he gained 30 percent of the vote in South Dakota and Montana later in the day. It takes 2,118 delegates to clinch the nomination.

The 46-year-old first-term senator will face John McCain in November election to become the 44th president. The Arizona senator campaigned in Memphis on Tuesday, and had no immediate reaction to Obama's victory.

Clinton stood ready to concede that her rival had amassed the delegates needed to triumph, according to officials in her campaign. These officials said the New York senator did not intend to suspend or end her candidacy in a speech Tuesday night in New York. They spoke on condition of anonymity because they had not been authorized to divulge her plans.

Top Democratic officials have been pushing for an end to a nomination battle that shattered fundraising and voter turnout records, but also exposed racial and gender divisions within the party that threatened to undermine its chances in the November election against McCain.

Obama's triumph was fashioned on prodigious fundraising, meticulous organizing and his theme of change aimed at an electorate opposed to the Iraq war and worried about the economy _ all harnessed to his own innate gifts as a campaigner.

Clinton campaigned for months as the candidate of experience, a former first lady and second-term senator ready, she said, to take over on Day One.

But after a year on the trail, Obama won the kickoff Iowa caucuses on Jan. 3, and the first-term senator became something of an overnight political phenomenon.

``We came together as Democrats, as Republicans and independents, to stand up and say we are one nation, we are one people and our time for change has come,'' he said that night in Des Moines.

As the strongest female presidential candidate in history, Clinton drew large, enthusiastic audiences.

Obama's were bigger still. One audience, in Dallas, famously cheered when he blew his nose on stage; a crowd of 75,000 turned out in Portland, Oregon, the weekend before the state's May 20 primary.

The former first lady countered Obama's Iowa victory with an upset five days later in New Hampshire that set the stage for a campaign marathon as competitive as any in the United States in the last generation.

As other rivals quickly fell away in winter, the strongest black candidate in history and the strongest female White House contender traded victories on Super Tuesday, the Feb. 5 series of primaries and caucuses across 21 states and American Samoa that once seemed likely to settle the nomination.

But Clinton had a problem that Obama exploited, and he scored a coup she could not answer.

Pressed for cash, the former first lady ran noncompetitive campaigns in several Super Tuesday caucus states, allowing her rival to run up his delegate totals.

At the same time, Democratic Sen. Edward M. Kennedy, a liberal lion and scion of a political family, endorsed the young senator in terms that summoned memories of his slain brothers, yet sought to turn the page on the Clinton era.

Kennedy said in a reference to former President Bill Clinton: ``There was another time, when another young candidate was running for president and challenging America to cross a new frontier. He faced criticism from the preceding Democratic president, who was widely respected in the party.''

Merely by surviving Super Tuesday, Obama exceeded expectations.

But he did more than survive, emerging with a lead in delegates that he never relinquished, and proceeded to run off a string of 11 straight victories.

Clinton saved her candidacy once more with primary victories in Ohio and Texas on March 4, beginning a stretch in which she won primaries in six of the final nine states on the calendar.

By then Obama was well on his way to victory, Clinton and her allies stressed the popular vote instead of delegates. Yet he seemed to emerge from each loss with residual strength, picking up new support _ including from one-time rival, former North Carolina Sen. John Edwards _ and countering with wins of his own.

There were moments of anger, notably in a finger-wagging debate in South Carolina on Jan. 21 in which the two ripped into each other's professional past and corporate affiliations.

And Bill Clinton was a constant presence and an occasional irritant for Obama. The former president angered several black politicians when he seemed to diminish Obama's South Carolina triumph by noting that Jesse Jackson, a civil rights leader and one-time presidential hopeful, had also won the state.

There were relatively few policy differences. Clinton accused Obama of backing a health care plan that would leave millions out, and the two clashed repeatedly over trade.

Yet race, religion, region and gender became political fault lines as the two campaigned from coast to coast.

Along the way, Obama showed an ability to weather the inevitable controversies, most notably one caused by the incendiary rhetoric of his former pastor, the Rev. Jeremiah Wright.

At first, Obama said he could not break with his longtime spiritual adviser. Then, when Wright spoke out anew, Obama reversed course and denounced him strongly.

Clinton struggled with self-inflicted wounds. Most prominently, she claimed to have come under sniper fire as first lady more than a decade earlier while paying a visit to Bosnia.

Instead, videotapes showed her receiving a gift of flowers from a young girl who greeted her plane.