plunge into the race issue in Philadelphia Tuesday at times sounded more like a sermon than a speech.
But beneath the personal anecdotes and historical allusions, it was a delicately crafted political statement - one that makes clear that Obama understands exactly how much peril he is facing.
Even before the Jeremiah Wright controversy erupted in recent days, voting patterns in several states made clear - for all the glow of Obama's reputation as a bridge-builder - how uneven his record really is when it comes to transcending deep racial divides.
The Philadelphia speech offered lines calculated to reassure all the groups with which he is most vulnerable.
For working class whites-whose coolness toward Obama helped tilt Ohio to- Obama spoke with understanding about why they dislike busing and affirmative action. "Like the anger in the black community, these resentments aren't always shared in polite company," he said.
For Hispanics, who have sided with Clinton in the vast majority of states this election, he lashed pundits scouring polls for signs of tension between "black and brown" and said the two communities face a common heritage of discrimination and inadequate public services.
Finally, Obama sought to connect with white Jewish voters - potentially one of the rawest nerves of all amid the Wright controversy - denouncing those blacks who see "the conflicts in the Middle East as rooted primarily in the actions of stalwart allies like Israel, instead of emanating from the perverse and hateful ideologies of radical Islam."
It will take weeks, at least until the April 22 Pennsylvania primary, to know whether all of Obama's political and cultural base-touching succeeded.
Even before that verdict arrives, the speech counts as a remarkable event - most of all for the specificity with which Obama discussed racial attitudes and animosities that politicians usually prefer to leave unmentioned.
Of his own candidacy, Obama said, "I have never been so naive as to believe that we can get beyond our racial divisions in a single election cycle, or with a single candidacy - particularly a candidacy as imperfect as my own."
Truth be told, Obama and his most fervent supporters often have acted as if he could end some of the most persistent divisions in American life by proclamation.
When pressed on racial questions, Obama usually invoked his own biography and achievements and appealed to America's hunger for unity. When pressed on a voting record that National Journal called the most liberal in the Senate, Obama dismissed ideological labels as "old politics."
The Wright uproar showed that there is no way to sneak race and ideology through customs, blinding skeptics with his life-story and phrase-making. The candidate will need to address these volatile topics directly.
But this was becoming clear even before the Wright story caught fire.
It is true that Obama won a majority of white voters - a precedent-shattering achievement for a black presidential candidate - in an array of states like Illinois, Iowa, New Mexico, Wisconsin, and Virginia.
But many of his recent victories came when he got the better end of highly polarized voting patterns. He lost the white vote, sometimes by gaping margins in states like Alabama (whites went 72 percent for Clinton to Obama's 25 percent), Maryland (52 to 42) and Louisiana (58 to 30). He compensated only with overwhelming support by black voters.
In Ohio, it was Clinton who benefited from the racial pattern in the voting. She took 64 percent of the white vote, according to exit polls. That was easily enough to offset his 87 percent of the black vote. Overall, she won the state by eight percentage points.
This result could haunt Obama. The past two general elections wee tipped by narrow GOP victories in Ohio and these rural whites are a prototypical swing bloc in elections stretching back decades. Obama failed to win more than 35 percent of the vote in 11 of the 12 rural counties that border Pennsylvania.
Obama's cross-racial and even cross-partisan support has been driven by a belief that he is a new-era politician, not defined by the grievances and ideological habits of an earlier generation.
Then came Wright, who Obama has described as an important mentor, suggesting that in important ways he is a product of familiar animosities. "Barack knows what it means to be a black man living in a country and a culture that is controlled by rich, white people. Hillary ain't never been called a n---," he thundered in a sermon played relentlessly on television and the web this past week.
Merle Black, an expert on southern voters at Emory University, said Wright is a "huge, huge problem."
"The new information, especially about his minister and his twenty-year association with this church, really undermines the message he's been delivering for the last year, it completely undercuts it," said Black.
Latinos have been an even tougher obstacle for Obama than whites. The only states where he has carried this group, Connecticut, Virginia, Illinois and Iowa, have relatively small Hispanic populations. Obama has worked hard to break down this bloc's preference for Clinton, a task that likely is set back by Wright.
"There is an older generation, U.S. born, of the Latino population who can identify more with the black community on these civil rights issues and can identify with where the reverend is coming from," said Angelo Falcón, president of the National Institute for Latino Policy. "There are also people who have not been here as long who are going to find the whole mix of the reverends' words totally alien."
Obama's problems with some Jewish voters also predated the Wright coverage. The Illinois senator lost the Jewish vote by double-digits in Florida, New York, New Jersey and Maryland. He has been the victim of both an unwanted endorsement (Louis Farrakhan) and a dirty e-mail campaign claiming falsely that he is a Muslim.
In some quarters, his support of Israel has been suspect, despite his outspoken support for the U.S. ally. Wright didn't do him any favors when he accused Israel of "state terrorism against Palestinians."
"Wright's comments make the job of supporting Obama in the Jewish community more difficult," said a Jewish Democratic leader who asked that he not be identified by name in order to share his views more candidly. "On a rational level, Obama should be an easy sell in the Jewish community. This stuff is based on pure fear-mongering. There has been a concerted smear campaign against Obama that has targeted the Jewish community, in emails and conservative blogs.
"Obama's speech is a powerful tool to be used in support of Obama," he continued, "but on balance this is an issue that could have a negative impact on the Jewish vote."
David Paul Kuhn contributed to this report.
By Jim VandeHei and John F. Harris