Former Attorney General Alberto Gonzales says Donald Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE is right to challenge the fairness a judge overseeing lawsuits against him.

“An independent judiciary is extremely important. But that value is not the only one in play here,” Gonzales wrote in a Saturday op-ed for The Washington Post.

"Equally important, if not more important from my perspective as a former judge and U.S. attorney general, is a litigant’s right to a fair trial,” he continued.

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“The protection of that right is a primary reason why our Constitution provides for an independent judiciary. If judges and the trials over which they preside are not perceived as impartial, the public will quickly lose interest in the rule of law upon which our nation is based.”

Trump on Thursday said U.S. District Judge Gonzalo Curiel’s Hispanic ethnicity is “an absolute conflict” in three civil fraud lawsuits against the billionaire.

He said Curiel’s “Mexican heritage” makes him partial because of Trump’s calls for a wall along America’s southern border with Mexico.

Gonzales on Saturday said Trump has reason beyond just race to doubt Curiel, who is American, will treat him fairly.

“As someone whose own ancestors came to the United States from Mexico, I know ethnicity alone cannot pose a conflict of interests. But there may be other factors to consider in determining whether Trump’s concerns about getting an impartial trial are reasonable.”

Gonzales said Curiel is a member of La Raza Lawyers of San Diego, which Trump aides say is affiliated with a national group vociferously opposing Trump, National Council of La Raza (NCLR).

The Washington Post on Saturday reported that NCLR is unaffiliated with La Raza Lawyers of San Diego. It added Curiel is not a member of NCLR.

Curiel has also appointed the Robbins Geller law firm to plaintiffs, he added, noting Geller is a donor to Democratic presidential front-runner Hillary Clinton Hillary Diane Rodham ClintonJeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Momentum growing among Republicans for Supreme Court vote before Election Day Warning signs flash for Lindsey Graham in South Carolina MORE.

“These circumstances, while not necessarily conclusive, at least raise a legitimate question to be considered,” said Gonzales, who was attorney general for former President George W. Bush.

“If [Trump’s] criticism is solely based on Curiel’s race, that is something voters will take into account in deciding whether he is fit to be president. If, however, Trump is acting from a sincere motivation to protect his constitutional right to fair trial, his willingness to exercise his rights as an American citizen and raising the issue even in the face of severe criticism is surely also something for voters to consider.”

Curiel is overseeing three lawsuits which allege Trump University defrauded students and saddled them with debt.

Trump has repeatedly touted positive reviews from other participants, saying courts will ultimately vindicate the for-profit real estate program.