The US Supreme Court, which began the civil rights revolution 50 years ago, may now end it.
It was a unanimous 1954 court decision, Brown v Board of Education, that set the American civil rights movement into motion.
That decision began a process of school desegregation that lasted twenty years.
Civil rights campaigners journeyed from Detroit to the Supreme Court
And it precipitated an era of civil rights activism in the 1960s led by Martin Luther King that led to changes in the law concerning voting rights, workplace discrimination, and university admissions.
On Tuesday veterans of the civil rights era, such as King's former aide Jesse Jackson, gathered in front of the Supreme Court to say that a ruling against affirmative action could set back the civil rights movement decades.
But now, Mr Jackson told a crowd of several thousand that "there are more blacks in prison than in college" and urged the US to fight for freedom in Michigan as well as Iraq.
Among those at the rally were several hundred students from the University of Michigan, where three students are challenging its admissions policy for unfairly discriminating against whites.
Most of the students who had travelled by bus overnight from the Ann Arbor campus to attend the rally supported affirmative action.
Jennifer Gratz (right) complained about Michigan's admission system
Jerry Reynolds, a student at Michigan's social work school, said his school had a special responsibility to fight for equal rights, and this was the "Roe v Wade" of civil rights - referring to the key abortion case decided by the Supreme Court in 1973.
Detroit civil rights campaigner Zora McKinney said she had come to Washington because this case was just "the tip of iceberg - jobs, housing would be next."
Former University of Michigan President Lee Bollinger told BBC News Online that "it would be a great pity" if the court rolled back 40 years of progress in racial diversity.
The high-ceilinged Supreme Court chamber was packed when the case began.
Some people had spent the night outside the building, to secure a coveted place at the hearing.
The case centres on three white students, two of whom were rejected from the University of Michigan and one who was turned down by the university's law school.
The three - Jennifer Gratz, Patrick Hammacher, and Barbara Grutter - were all present in court.
They say the decisions to reject them amounted to illegal discrimination by the university, and that if they had been a member of a minority group they would have been accepted.
Addressing the press pack outside the court, Ms Gratz said that she was rejected simply because of her skin colour.
"Court records show that if I had been black, Hispanic or Native American, I would have had a nearly 100% chance of admission with my grades and record."
The university has countered that race was only one factor in the process and that "affirmative action" - whereby students from ethnic minorities are given extra points during the admissions process - provides a more diverse student body of benefit to all races.
Within the Supreme Court, now bitterly divided between liberals and conservatives, the most striking fact in the courtroom was the appearance of the US Government on the side of the plaintiffs.
The administration's chief law officer, Solicitor General Theodore Olson, appeared to support the students' case and condemn the Michigan admissions plan as a "thinly disguised quota" which has been unconstitutional since a previous court ruling in 1978.
George W Bush had previously described affirmative action as still resembling "quota systems that... exclude people from higher education... are divisive, unfair and impossible to square with the Constitution".
But Mr Olson was careful not to rule out the use of race entirely in admissions, saying that the government was "reluctant to say never".
To some observers, it is all part of the Bush administration's "southern strategy" to gain re-election by appealing to disaffected white democratic voters in the South and West ahead of the 2004 election.
In oral arguments before the Supreme Court, each side has 30 minutes to present their case - but are often interrupted by questions from justices.
These are closely watched for clues as to how they will finally vote.
On the liberal side, Justice Stephen Breyer said there were arguments that schools should reach out to people of all races, to train minorities to be leaders in law, military, government and other fields.
For the conservative side, Justice Antonon Scalia said that he thought the Michigan system amounted to a quota, and questioned whether it furthered racial harmony if it upset many people who fell foul of its provisions.
Justice Sandra Day O'Connor, considered a key swing vote on this issue, said law schools make many choices in picking students, and
she wondered aloud why they could not also consider race.
And Justice Anthony Kennedy, another key vote, asked if colleges should be concerned when blacks and Hispanics are underrepresented, making up a small percentage of students.
In a rare question, Justice Clarence Thomas, the only black member of the Supreme Court, asked whether affirmative action was helping or hindering progress towards racial harmony.
A split decision is expected by the court before the end of its current session.