Washington (CNN) The Justice Department this week signaled it would pursue Asian-American students' complaints of bias in admissions at Harvard University, a move that could ultimately alter the future of affirmative action nationwide.

Four decades after a landmark US Supreme Court ruling, affirmative action that brings diversity to college campuses has become entrenched. Yet it has been continually challenged, upheld by one-vote margins at the US Supreme Court.

For nearly three years, Harvard has been fighting a lawsuit targeting its admissions practices brought by a small advocacy group that enlisted Asian-American students. They claim the Ivy League campus caps the number of high-achieving Asian Americans as part of "racial balancing" that favors African Americans and Hispanics.

The advocates behind the case have a record of related litigation, and their long-held goal has been to end nationwide affirmative action programs designed to help blacks and other traditionally disadvantaged minorities.

Now it appears the Trump administration could throw its weight into the case or, even more potently, launch its own lawsuit against university policies.

Either move could support a broader effort, seen in the Harvard lawsuit, to reverse a 1978 Supreme Court decision that allowed colleges to consider an applicant's race as one of many factors in admissions, but forbade quotas. The action would play to a conservative base that has long abhorred practices that offer a boost to racial minorities, potentially at the expense of whites.

So far, the Supreme Court has rejected challenges, but just barely.

In 2016, the Supreme Court endorsed a University of Texas program that favored blacks and Hispanics by a vote of 4-3. (Two of the nine justices did not participate.) Abigail Fisher, a white student from suburban Houston, spurned by the state's flagship Austin campus, had been recruited for the case by the same advocates behind the Harvard lawsuit.

New DOJ involvement could ratchet up the pressure on universities like Harvard that place a premium on racial and ethnic diversity and ramp up the stakes for some Asian-American students.

In the Harvard lawsuit dating to November 2014, the plaintiffs say Harvard holds Asian-American applicants to tougher academic criteria as a way to limit their admissions, which would violate federal civil rights law forbidding discrimination based on race.

Harvard has rejected allegations of unlawful racial balancing. Melodie Jackson, a Harvard spokeswoman, said in a statement this week that "Harvard remains committed to enrolling diverse classes of students. Harvard's admissions process considers each applicant as a whole person, and we review many factors."

What can the Justice Department do?

The scope of possible Trump administration involvement is not clear. Its options would cover administrative moves, such as requesting detailed student-selection data, to an outright court challenge to a university's admissions practices based on federal civil rights law or the Constitution's equality guarantee.

DOJ spokeswoman Sarah Isgur Flores said the department was looking for lawyers to investigate a lingering administrative complaint filed in May 2015 by a coalition of 64 Asian-American groups.

She did not name the university, but in May 2015 a coalition of 64 Asian-American groups went public with their claim of bias at Harvard. It is separate from the Harvard lawsuit, but some the grounds in the complaint were lifted from the Harvard case.

This week's DOJ statement followed a report in The New York Times that the department's civil rights division was seeking lawyers, according to an internal document , to work on "investigations and possible litigation related to intentional race-based discrimination in college and university admissions." The Times said the administration was putting new resources into suing universities over "policies deemed to discriminate against white applicants."

Flores said the Times' broader description of the administration's agenda was "inaccurate."

Behind the Harvard lawsuit

The Harvard lawsuit was brought by a group called Students for Fair Admissions, run by Edward Blum, who for decades has been rounding up white plaintiffs to challenge racial policies. As part of the new emphasis on Asian-American plaintiffs, Blum arranged a similar lawsuit, also filed in November 2014, against the University of North Carolina.

Litigants in both cases have been gathering documents and interviews to support their respective legal positions, and no trial dates have been set.

Blum, who resides in Maine, has been engineering lawsuits against government racial policies since the early 1990s. He began when he lived in Texas and lost a bid for a congressional seat in a racially gerrymandered district.

Blum, and some of the same conservative attorneys, also initiated the lawsuit that led to the 2013 Supreme Court ruling in Shelby County v. Holder curtailing the reach of the Voting Rights Act of 1965.

Blum said he would welcome DOJ participation in the allegations against Harvard.

Jon Greenbaum, chief counsel with the Lawyers' Committee on Civil Rights, has closely followed the Harvard case on behalf of African American, Hispanic, and Native American students. The Lawyers' Committee has argued in court filings that blacks and other racial minorities were the true target of the litigation because of the underlying claim that all racial preferences are unlawful.

If the Trump administration puts federal resources toward opposition to affirmative action, Greenbaum said, it could dramatically shift the playing field.

The Department of Education, which oversees college and university policy through its federal funding, would be able to collect data on their internal workings that outside litigants cannot obtain.

And if the administration mounts its own lawsuit against a university, Greenbaum notes, it would depart from past DOJ practice and break new ground in the longstanding battle over race on campus.