Donald Trump’s week-long tear against federal judge Gonzalo Curiel has upset many in his own party, including House Speaker Paul Ryan (R-WI) and Senate Majority Leader Mitch McConnell (R-KY).

But at least one prominent Republican thinks its worth considering Trump’s claim of Curiel’s “bias” against him: Former attorney general Alberto Gonzales.

“Regardless of the way Trump has gone about raising his concerns over whether he’s getting a fair trial, none of us should dismiss those concerns out of hand without carefully examining how a defendant in his position might perceive them — and we certainly should not dismiss them for partisan political reasons,” Gonzales wrote in a Washington Post op-ed published Saturday.

Trump has said that the Indiana-born Curiel should be recused from overseeing a fraud investigation into Trump University because his “Mexican heritage” presents a “conflict of interest.”

Gonzales acknowledges Trump’s ethnicity-based explanation at the start of his op-ed, then launches into a list of reasons why Trump may legitimately feel that Curiel won’t give him a “fair trial.”

According to Gonzales, one reason, which Trump’s own aides have floated, is that Curiel is a member of La Raza Lawyers Association, a Latino lawyers group. Gonzales floats their unsubstantiated claim that the group is tied to La Raza, a non-profit Latino advocacy organization that has spoken out against Trump’s anti-immigrant rhetoric.

“The two groups appear to be unaffiliated, but Trump may be concerned that the lawyers’ association or its members represent or support the national advocacy organization,” Gonzales suggested.

Another cause for suspicion, Gonzales said, is that Curiel appointed a law firm whose head has donated to Hillary Clinton to represent the plaintiffs in the Trump University case.

“It might not be unreasonable for a defendant in Trump’s position to wonder who Curiel favors in the presidential election,” Gonzales wrote. “These circumstances, while not necessarily conclusive, at least raise a legitimate question to be considered.”

Gonzales, whose family also immigrated to the U.S. from Mexico, did note that Curiel’s Mexican heritage “would not be enough to raise a question of bias.”

The former attorney general served during the George W. Bush administration. He endorsed the legal authorization for the use of torture techniques in the Iraq and Afghanistan wars. Gonzales resigned from office in 2007 over the scandal ignited by the dismissal of a number of U.S. attorneys deemed insufficiently loyal to the Bush administration.