Ahmed Aziz, standing outside McCoy's Auto Repair in North Philadelphia, needed but three words to describe how he's going to vote next week:

"Obama, Obama, Obama," the 58-year-old said emphatically. "I'm done with the Clintons."

Shop owner Saadiq Muhammed, 60, nodded his assent. "How could any black person," he wondered, "not vote for Obama?"

Twenty-four hours and 28 blocks away, Jackie Purnell, 60, offered an answer:

"She's sincere," she said, flush with excitement from having just seen Sen. Hillary Rodham Clinton during a rally at the West Philadelphia YMCA. "A lot of black people don't do their history. They say, 'Oh, it's a black man and let's vote for him.' To me, Obama just popped out of nowhere."

As Pennsylvania speeds toward Tuesday's Democratic primary, Sen. Barack Obama's campaign is hoping to pull off an unexpected, come-from-behind win - or at least deal the Clinton effort a hard blow by placing a close second. A CNN analysis had Clinton's lead down to 4 percentage points - before the flap over Obama's comments about "bitter" Pennsylvanians helped nudge the margin to 6. A Philadelphia Daily News/Franklin and Marshall College poll released Wednesday showed the same margin.

What's unchanged is that to finish strong, the Illinois senator will need heavy if not historic support from African American voters, particularly in the Philadelphia region.

He might not get it.

In interviews with local voters, it's plain that black support for Obama is deep, strong, heartfelt - but hardly universal.

"There are black people who have connections to the Clintons who are going to remain loyal," said F. Carl Walton, who teaches political science at Lincoln University, the historically black school in Chester County. "All black people are not going to vote for him because he's black. . . . At the end of the day, people are going to look at the issues."

For instance, Philadelphia's black mayor, Michael Nutter, has endorsed Clinton, saying "her priorities are the right priorities" for the city.

Some African American voters say having to choose between two attractive, history-making candidates is confounding. They're paying attention to the political ads now blanketing the airwaves, where Obama is outspending Clinton at least two to one.

Listen in on conversations among black voters, and you'll hear debates about whether America is more sexist or more racist. Listen in, and you'll hear plenty of talk about phantom sniper fire in Bosnia, little about the charged sermons of the Rev. Jeremiah Wright, and worries about jobs and the future.

The Rev. Isaac Miller, 65, is pastor of the renowned Church of the Advocate in North Philadelphia, long a center of social action. He was leaning toward Obama but still undecided as the candidate posted wins and near-wins in the early primaries. Now, Miller said, he's "seriously in his corner."

To Miller, the grandson of a slave, Obama represents the "second viable opportunity to step beyond race in this country. Of course, the first was with Martin."

He wants change: In race relations. In rich-poor divisions. In the way the United States exerts its military and economic might around the globe.

"Part of my hope for Obama is that people throughout the world will say, 'Well, the United States has decided it can step beyond bondage in relation to race in its country. Maybe they can step beyond bondage in relation to me.' "

At stake are 158 delegates in a state that seems tailor-made for Clinton, who draws support from blue-collar, women, and older voters. Pennsylvania has higher-than-usual union membership: 13.5 percent of wage earners, compared with 12 percent nationally. Only Florida and West Virginia have older populations.

More than half of Pennsylvania's voting-age adults are female. And while Philadelphia is 44 percent African American, statewide that figure drops to 11 percent.

Polls show Obama claiming 75 percent of the black votes in Pennsylvania.