By JOHN HARWOOD
The New York Times

If Tuesday’s election were confined to white America, polls show, Senator Barack Obama would lose.

And yet Mr. Obama’s strength across racial lines lies at the heart of his lead in the polls over Senator John McCain heading into Election Day. Remarkably, Mr. Obama, the first black major party presidential nominee, trails among whites by less than Democratic nominees normally do.

America’s political parties grew decisively polarized by race after 1964, the year President Lyndon Johnson signed civil rights legislation that his Republican presidential opponent, Barry Goldwater, opposed. Since then, election pollsters estimate, Democratic nominees have averaged 39 percent of the white vote. In last week’s New York Times/CBS News poll, Mr. Obama drew 44 percent support among whites — a higher proportion than Bill Clinton captured in his general election victories.

Analysts ascribe that success to changing racial attitudes, Mr. Obama’s deftness, Republican missteps and the economic crisis. Whatever the cause, when combined with his two-to-one edge among Hispanics and his 10-to-1 edge among blacks, it has given him a national election-eve lead.

The race is not over, and Election Day could bring surprises. And Mr. McCain is capturing a majority of the white vote, according to these same polls. Yet population shifts have made racial and ethnic diversity an unavoidable fact of American life. When Ronald Reagan won re-election in 1984, whites made up 86 percent of the electorate; by 2004, they had dropped to 77 percent.

With that backdrop, some observers say racial attitudes have diminished as an independent force, fading into the broader fabric of cultural concerns that shape voters’ choices like religion, abortion and gun control.

“Anybody who votes against Barack Obama because of the color of his skin, the Republicans would have gotten on another cultural issue,” said David Saunders, a consultant in Virginia who advises Democratic candidates on attracting white rural and working-class voters.

The presidential historian Michael Beschloss credits Mr. Obama with reprising the approach adopted by John F. Kennedy in his 1960 breakthrough as the first Roman Catholic to win the presidency. “He was running to be president of all the people, not president of a faction,” Mr. Beschloss said.

A recent NBC News/Wall Street Journal poll documents Mr. Obama’s success in making that case. Asked whether an Obama presidency would favor the interests of blacks over other Americans, 8 in 10 whites said it would not.

For Democratic strategists who have spent their careers laboring to regain white voters’ allegiance, that alone is a striking achievement. In the mid-1980s, research by the pollster Stan Greenberg in Macomb County, Mich., concluded that middle-class whites resented the “raw deal” they received from a political debate in which Democrats appeared focused on racial minorities and the poor.

Like Mr. Greenberg’s client Bill Clinton in 1992, Mr. Obama has emphasized broad-gauged assistance for the middle class. “He’s managed to campaign in ways that may not have changed their world view but have allowed them to put those feelings aside,” Mr. Greenberg said. He added with a note of bemusement, “Maybe he has crossed over into Tiger Woods territory.”

Frustrated Republicans see Mr. Obama’s steady performances on the stump and in debates as only part of the explanation for his surprising level of white support. Just as responsible, some argue, is that President Bush’s unpopularity in threatening economic times has veered close to Herbert Hoover territory. “You’ve got to give Obama an awful lot of credit for his likability,” said Tom Slade, a former Florida Republican Party chairman, who abandoned his own Democratic allegiance in 1964 in the early phase of white conservatives’ political migration. More important, he said, “We have done a miserable job of managing the affairs of government.”

In the early 1990s, the political reporter Peter Brown wrote “Minority Party,” a book exploring the pitfalls of the Democrats’ identification with the interests of African-Americans. He credited Mr. Obama with providing “a comfort zone” for white voters, but pointed to the major boost he received this fall from the financial crisis on the watch of a Republican president.

“The most important color is green,” said Mr. Brown, now assistant director of the Quinnipiac University Polling Institute. “When Lehman Brothers went under, this thing changed dramatically. People are just terrified about their financial futures.”

In the spring, some Democratic strategists feared Mr. Obama might be crippled in states where he lost working-class white primary voters decisively to Senator Hillary Rodham Clinton. In Ohio, carried by Mr. Bush in 2000 and 2004, polls now show Mr. Obama is competitive; in Pennsylvania, a top target for Mr. McCain, he is ahead in the polls.

With a message muting racial concerns, Mr. Obama didn’t begin his presidential bid with overwhelming strength among blacks; that came only after he defeated Mrs. Clinton in the white-dominated Iowa caucuses. “Ironically, the biggest difficulty about race for Obama was the doubts among African-Americans about his ability to succeed in the nominating process,” said Tad Devine, a top strategist for Al Gore in 2000 and John Kerry in 2004.

“It’s amazing to me — almost unreal,” Representative John Lewis of Georgia said. Earlier this fall Mr. Lewis, the civil rights movement veteran, accused Mr. McCain’s campaign of “sowing the seeds of hatred” in a way that was reminiscent of George Wallace during the 1960s, an attack that the Republican nominee called “brazen and baseless” and that Mr. Obama distanced himself from.

More recently, Mr. Lewis added, the campaign has made him “sort of sad” since leaders of that movement, including the Rev. Dr. Martin Luther King Jr. and President Johnson, cannot witness Mr. Obama’s candidacy.