Washington (CNN) The most dramatic showdown during the first Democratic debate was between Sen. Kamala Harris and former Vice President Joe Biden over his decades-long opposition to desegregation busing.

But on the sidelines of the re-litigated fight over busing -- and off the stage that second night -- was another candidate who waded into the busing debate in the 1970s on the opposite side of Biden: Massachusetts Sen. Elizabeth Warren.

Warren's law review article sheds light on a previously unexplored early career stance on busing that contrasts with Biden's approach during the same time period. Biden defended his past position in an exclusive interview with CNN this week.

At the time, busing was a highly unpopular policy in the US. Public polling in the mid-1970s found about three-quarters of Americans opposed it.

Warren's communications director Kristen Orthman told CNN that Warren stood by the article today and supported the Strength in Diversity Act, a bill which would "support voluntary local efforts to increase racial diversity and socioeconomic diversity."

"In addition, if localities are not taking action to desegregate schools, Elizabeth believes the federal government has a constitutional obligation to step in to deliver on the promise of Brown v. Board, including, if necessary, busing," Orthman said.

"She has plainly done her homework"

Warren's decision to write about education in her first published law review article would mark the beginning of a long career in both education, as a law professor, and politics as a senator and presidential candidate.

Her first article, according to Justin Driver, a professor of law at Yale School of Law, showed a remarkable understanding of the complexities in education law.

It was an "extremely accomplished piece of scholarship by a student," said Driver. "She has plainly done her homework."

In the article, Warren predicted that de facto segregation -- segregation that occurs not because it was institutionalized by the government but because of social norms, prejudices and self-selection -- and de jure -- segregation that existed because of laws that mandated racial segregation -- had been silently "reaffirming" by the court and would take over American public schools.

The isolation of minorities in urban centers, Warren wrote, and a shrinking tax base to finance public education would lead to facilities that are inferior in "student-teacher ratios, and other educational advantages" for minority students. For Brown v. Board of Education to have meaning in northern urban centers, Warren said that "effectively separate schools, even if equal, and certainly if unequal, are condemned by the Constitution, regardless of the reason for the separation."

The most "devastating" desegregation case in Supreme Court history

In the 1970s, a class-action lawsuit filed by the NAACP alleged that the Detroit Board of Education and officials from the state of Michigan, including Gov. William Milliken, maintained racial segregation within the city's school system. The lawsuit, Milliken v. Bradley, demanded a plan to desegregate a nearly all-black Detroit school district by integrating with the 53 other school districts in the area. The district court concluded the state's practices were unconstitutional and issued an order to desegregate the school districts by busing students from nearby school districts. The Sixth Circuit Court of Appeals affirmed the district court's ruling.

However, the Supreme Court reversed the decision of the lower courts in Milliken v. Bradley. The Court ruled 5-4 that a majority-black school district like Detroit could not bus students from majority-white suburban school districts to Detroit to desegregate the city's schools, unless those suburban districts were also engaged in unlawful segregation practices. In short, a district court could not fashion an interdistrict remedy to cure an intradistrict constitutional violation.

"Milliken v. Bradley was the most devastating desegregation decision in the history of the United States Courts," said Kimberly Robinson, a professor of law at the University of Virginia School of Law.

Robinson said that Milliken made solutions to segregation in Northern cities nearly impossible.

As white flight took hold of cities across America in the 1950s and 1960s, cities and suburbs became racially homogenous and their school districts reflected populations. The Supreme Court then mandated that any interdistrict violations would have to be shown before any interdistrict remedies, like busing, could take place. With the Court's new mandate for interdistrict violations, the decision "handcuffed" federal district courts from intervening, said Robinson.

Warren weighs in

Warren also seemed to recognize the significance of Milliken in her law review article. She argued that without proper oversight from the federal court system, she wrote, the burden of desegregation has fallen on to black communities.

"It has been black parents, children, and organizations committed to desegregation who have shouldered the major part of the burden...Clearly, the burden for enforcing the Brown right has been misplaced," Warren wrote.

Warren wrote that the Milliken ruling, coupled with another ruling that upheld the state system of financing public schools by local taxes, "will lead to central-city schools which are inferior in facilities, student-teacher ratios, and other educational advantages because the funding is not commensurate with that available for suburban schools."

Erika K. Wilson, a professor of public policy at the University of North Carolina School of Law, said that Warren's predictions for what would occur in the American education system largely came true and that her view was closely aligned with Justice Thurgood Marshall, who wrote a dissenting opinion in Milliken. America's school systems would become "irreparably segregated," said Wilson.

Warren, noted Wilson, might have been out of step with her contemporaries at the time, and particularly "out of step" with white Americans who were "tired" of the decades-long battle to integrate public schools.

A contrast with Biden

As Warren was writing on busing, at the same time in the 1970s, Biden, as a young senator, stood against busing in places with de facto segregation like Detroit. He criticized the courts for using the terms desegregation and integration interchangeably, seeming to side with the very Supreme Court decision Warren wrote against.

. Biden further explained that he supported desegregation by any legal means at hand -- including busing in cases where a school district has upheld racially segregated district lines. However, he did not support busing for all-white or all-black school districts "because of historical pattern not involving segregation practices disapproved by a court." "There is a conceptual difference between desegregation and integration," Biden said to Wilmington, Delaware's, daily newspaper, The News Journal, in 1975 . Biden further explained that he supported desegregation by any legal means at hand -- including busing in cases where a school district has upheld racially segregated district lines. However, he did not support busing for all-white or all-black school districts "because of historical pattern not involving segregation practices disapproved by a court."

The Morning News, a Wilmington newspaper, in 1977. "But busing is not the way. It was a bad idea in theory, and it has turned out to be even worse in practice." "Nobody is more committed to equal educational opportunity than I," said Biden toThe Morning News, a Wilmington newspaper, in 1977. "But busing is not the way. It was a bad idea in theory, and it has turned out to be even worse in practice."

"The majority of particularly white Americans who were tired of school desegregation saw (Milliken) as a victory and a good thing," Wilson said.

But Warren did not. She said the decision "could thus be the 'separate and unequal' schools" and called on Congress to intervene.

"If the Court cannot or will not develop a judicial remedy for urban school segregation, then Congress must. Equal educational opportunity requires the combined efforts of the judiciary, the legislative branch, and the administrative departments of the executive branch," Warren concluded.