With the racially tinged Democratic race drawing to an awkward close, Barack Obama and John McCain face the challenge of winning over "Hillary Democrats" _ the white, working-class voters who favored the former first lady over Obama's historic candidacy.

Obama and McCain clearly have set their sights on each other, a recognition of the long odds Clinton faces in trying to capture the Democratic presidential nomination. The McCain campaign figures some of her supporters might be up for grabs and won't necessarily vote Democratic in the general election in November.

"I've been saying for a year that you never count a Clinton out, but now people are laughing at me so I guess I've got to stop," McCain strategist Charlie Black said Friday. But if you look at the blue-collar Democratic votes that Mrs. Clinton's been getting and then look at their opinions of Obama in these public polls, there's clearly an opportunity for McCain."

Clinton won more than two-thirds of the white voters without college degrees in the last three primaries _ Pennsylvania, North Carolina and Indiana _ according to exit polls conducted for The Associated Press and the television networks. When those Clinton supporters were asked who they would vote for in an Obama-McCain matchup, just fewer than half said they would support Obama. Three in 10 said they would vote for McCain and the rest said they wouldn't vote for either.

Shrugging off those numbers, Obama spokesman Bill Burton expressed confidence that Democratic voters will unite behind the nominee. He argued that the Illinois senator also would attract "droves of independent voters and disaffected Republicans that he has already won over all across the country."

Clinton is trying to use her advantage with white working-class voters to persuade party leaders to disregard Obama's overall advantage at the ballot and nominate her. Her campaign circulated a letter Friday from 16 members of Congress arguing she's the strongest candidate to have at the top of the ticket in the fall because she has won most rural and suburban congressional swing districts.

Clinton told USA Today in an article published Thursday that AP exit polls "found how Senator Obama's support among working, hardworking Americans, white Americans, is weakening again, and how whites in both states who had not completed college were supporting me."

"There's a pattern emerging here," she said.

Republican pollster Whit Ayres said that based on focus groups he has conducted in swing states, including Missouri, Michigan and Florida, Clinton's claim that she would do better than Obama with blue-collar white voters is believable.

He said those voters support her because of the prosperous economic times they experienced when her husband was president. He also said they are uncomfortable with Obama because of his relationship with the Rev. Jeremiah Wright, who created a furor with his divisive comments, and questions about Obama's patriotism.

"It's cultural," Ayres said.

The older those voters are, the more likely they are to support Clinton. Whites without college degrees under 30 support Obama, although to a lesser extent than the college educated.

In the general election, Democrats trying to attract white, working-class voters immediately start at a disadvantage. The party's presidential candidates have not won a majority of white voters in more than three decades, according to exit polls over the years. The only Democrat to come close was Bill Clinton, who lost to Bob Dole among whites by 3 percentage points in 1996 and to President George H.W. Bush by 1 point in 1992.

This year, whites who do not have college degrees lean slightly toward the GOP, according to an Associated Press-Yahoo News survey conducted last month, with 43 percent calling themselves Republicans and 38 percent considering themselves Democrats.

Ruy Teixeira, author of "America's Forgotten Majority: Why the White Working Class Still Matters," said Democrats have a better chance of winning more votes from this demographic this year because of the troubled economy, the war in Iraq and rising health care costs and millions who remain uninsured.

"These are voters who haven't been doing too well throughout the whole Bush administration and now are really sort of beside themselves, don't have a lot of faith in the Republican brand of economic management," said Teixeira, a Democrat not supporting either Obama or Clinton. "The question is can McCain push other issues in such a way as to prevent the Democrats from taking advantage of their built-in advantage on the issues that are going to be current in this election."

Black said if McCain is to win over any "Hillary Democrats," he'll have to work for them and earn them, and he plans to do that.

"I think you'll see particularly his economic message and his health care message in very populous terms, and that he'll be talking to and meeting with people in that category," Black said. "A lot of these voters are conservative. A lot of them believe in a strong national defense."

They also believe in their guns, said strategist Mudcat Sanders, who advises Democrats on rural issues.

"He's got one thing he's got to do and he's got to say it clearly. He's got to say, `I'm not going to take anybody's gun,'" Sanders said. Obama has done that at times, such as when he was campaigning for Western voters. "It's not a litmus test. It shows you are in line with the culture."

Sanders said if Obama does that and spends time getting to know rural voters, he can win them over.

"He's got to embrace the culture is what he's got to do," Sanders said. "The boy's IQ looks like Pete Rose's liftime batting average. It's off the charts. But at the same token, that comes off to us as big city. The big city thing John Kerry never could shake, I think, is Obama's problem right now. But I think he can get those voters and lot more if he just gets out there among the people so they can get to know him."

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Associated Press Writer Alan Fram contributed to this report.

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EDITOR'S NOTE: Nedra Pickler has covered presidential politics for The Associated Press since 2002.