An overwhelming racial gap divides public attitudes on the Trayvon Martin case and the fairness of the criminal justice system overall, marking the difficulties in the national conversation on race that Barack Obama sought last week to encourage.

By a vast 86-9 percent, African-Americans in a new ABC News/Washington Post poll disapprove of the verdict acquitting George Zimmerman of criminal charges in Martin's death, while whites approve by 51-31 percent. Blacks, by 81-13 percent, favor federal civil rights charges against Zimmerman; whites are opposed, 59-27 percent.

See PDF with full results and charts here.

More broadly, 86 percent of African-Americans say blacks and other minorities do not receive equal treatment as whites in the criminal justice system. Again, far fewer whites, 41 percent, share that view - a division that has prevailed, to varying degrees, in ABC/Post polls dating back 20 years.

In another measure demonstrating racial differences on the case, 87 percent of blacks in this poll, produced for ABC by Langer Research Associates, call Martin's shooting unjustified. Just a third of whites agree; another third call it justified, with the rest unsure.

Hispanics align more with blacks on these issues, albeit to a lesser extent. Six in 10 Hispanics say minorities are deprived equal treatment in the justice system. Half disapprove of the Zimmerman verdict, double the number who approve. Twice as many Hispanics see the shooting as unjustified than as justified (though half feel they don't know enough about it to say). And 58 percent of Hispanics favor civil rights charges against Zimmerman, more than double the number who oppose that step.

The U.S. Justice Department is evaluating whether to level such charges against Zimmerman, a neighborhood watch volunteer in Sanford, Florida, who fatally shot Martin, an unarmed black teenager, in February 2012. Zimmerman, claiming self-defense, was acquitted in state court July 13. Demonstrators in dozens of cities protested the verdict Saturday.

Obama, in the most extensive remarks of his presidency on race relations, last week described the experiences that inform many blacks' views on the issue and urged Americans to "do some soul-searching" on both their own attitudes and the nation's progress on racial equality.

Given the very different starting points between racial and ethnic groups, this poll underscores the challenges in addressing the topic. In polling since 1992, anywhere from 73 to 89 percent of African-Americans have said blacks do not receive equal treatment as whites in the criminal justice system. Today's level is just three points from the high, set in April 1992 after a jury acquitted four Los Angeles police officers in the beating of Rodney King.

Views among whites on this question have fluctuated, but always have been strikingly different from those of blacks. In spring 2012, amidst a debate on whether or not Zimmerman should be charged with a crime, whites divided, 44-49 percent, on whether minorities receive equal treatment or not. Today, with the charge filed and the case tried, more whites, 54 percent, say minorities do receive equal treatment. That nearly matches the average among whites (51 percent) in eight polls spanning the past 20 years.

Whites do not broadly see Martin's shooting as justified; rather, as noted, they divide, with about a third calling it justified, a third saying it was unjustified and a third saying they don't know enough about it to come to a conclusion. Given the trial and verdict, however, the number of whites who see the shooting as justified has swelled from 5 percent in April 2012 to 33 percent now, while the number who feel they can't say has plummeted by 24 percentage points.

Hispanics remain especially apt to feel they can't say whether the shooting was or wasn't justified; 50 percent do so. Of the rest, 34 percent call the shooting unjustified, while many fewer, 16 percent, see it as justified.

There are differences among other groups. Adults younger than 40 are more apt than their elders to doubt that minorities receive equal treatment. College-educated whites are somewhat more apt to see unequal treatment than are those who lack a college degree. And there are sharp partisan and ideological divisions: Seven in 10 Democrats and liberals think minorities are denied equal treatment; independents and moderates roughly divide, while Republicans and conservatives are much more likely to think minorities are equally treated in the criminal justice system.

Many of these divisions also are reflected in views of the Martin case, including whether the shooting was justified, views on the verdict and opinions on whether or not Zimmerman should be charged with violating Martin's civil rights. In one striking division that reaches beyond race and ethnicity, 58 percent of 18- to 29-year-olds favor civil rights charges against Zimmerman, the only age group in which a majority holds this view. Among senior citizens, by contrast, just 25 percent agree.

METHODOLOGY - This ABC News/Washington Post poll was conducted by telephone July 18-21, 2013, in English and Spanish, among a random national sample of 1,002 adults, including landline and cell-phone-only respondents. Results have a margin of sampling error of 3.5 points, including design effect. Partisan divisions are 31-21-37 percent, Democrats-Republicans-independents.

The survey was produced for ABC News by Langer Research Associates of New York, N.Y., with sampling, data collection and tabulation by Abt-SRBI of New York, N.Y.