Defying critics across the political spectrum,
Trump told CBS News that U.S. District Judge Gonzalo Curiel was "a member of a club or society very strongly pro-Mexican" and thus cannot be impartial with a presidential candidate proposing a border wall.
"If it were a Muslim judge, would you also feel like they wouldn't be able to treat you fairly because of that policy of yours?" news anchor John Dickerson asked Trump in a "Face the Nation" interview that aired Sunday.
"It's possible, yes," said Trump, who has called for a temporary ban on Muslims entering the United States. "Yeah, that would be possible, absolutely."
Even for a man who launched his candidacy by accusing Mexico of sending rapists and drug dealers across the border, Trump's recent remarks about Latinos and Muslims were extraordinary, sparking fresh accusations of bigotry.
His comments came after months of violent and racially charged clashes at his rallies between his overwhelmingly white supporters and protesters, many of them Latino or African American. Riot police are routinely deployed outside Trump's events to keep the two sides apart, a sign of potential trouble at next month's Republican National Convention in Cleveland.
Aside from the social implications in a nation with a wrenching history of racial strife, Trump’s escalating attacks on the judge have unsettled top
GOP allies quickly criticized Trump for charging that the judge's Mexican ancestry poses a conflict of interest.
House Speaker Paul D. Ryan, who begrudgingly endorsed Trump on Thursday, said Friday that he disapproved of Trump's remarks.
Senate Majority Leader Mitch McConnell said Sunday on NBC's "Meet the Press" that "I couldn't disagree more with what he had to say." He refused to answer whether he saw Trump's attacks as racist.
Former House Speaker Newt Gingrich called the statements "inexcusable," saying they were "one of the worst mistakes Trump has made."
"Trump has got to, I think, move to a new level," Gingrich told Fox News on Sunday. "This is no longer the primaries. He's no longer an interesting contender. He is now the potential leader of the United States, and he's got to move his game up to the level of being a potential leader."
Trump's unwillingness so far to heed such warnings underscores his lack of self-restraint as he shifts focus to the broader electorate. He has stepped up his belligerence toward the news media, describing reporters as scum, sleaze and bloodsuckers in recent days.
Curiel, born in Indiana to Mexican immigrants, is presiding over a San Diego fraud lawsuit against the candidate and his defunct real estate school, Trump University. A former narcotics prosecutor, Curiel was appointed to a state judgeship by former Republican Gov. Arnold Schwarzenegger and to the federal bench by President Obama. Trump has accused the judge of showing bias against him, but only in the last few days has he identified Curiel's ethnicity as the reason.
Political scientist Julia Azari of Marquette University in Milwaukee said it was easy to forget that the kind of overt prejudice expressed by Trump was the norm in American politics before the civil rights movement took hold in the 1950s.
"It's only fairly recently that these things have been frowned on in public discourse, and we've assumed that politics and public life would be inclusive regardless of race, gender or ethnicity," she said. "You don't erase a history of oppression or exclusion in 60 years."
As Trump wrapped up a California campaign swing on Friday, he stirred up more charges of racism at a rally in Redding when he called a man in the crowd "my African American."
Trump was praising a black supporter who had slugged and kicked a protester at his March rally in Tucson, calling him "a great guy," when he interrupted the story to point to an African American in his mostly white audience.
"Look at my African American over here," Trump shouted. "Look at him. Are you the greatest?"
Critics on social media charged that Trump's language evoked slavery.
"Unbelievable," Democratic strategist Donna Brazile wrote on Twitter.
But it's Trump's attack on Curiel that has drawn the most attention.
Democratic presidential candidate Hillary Clinton rebuked Trump on Sunday for what she called his "ethnic slurs and rants," and denounced him for "bigotry" in a scathing speech last week detailing her case against him. She pursued that line of attack as she campaigned across California, highlighting Trump's criticism of Curiel.
"This is not just another outlandish, insulting comment from Donald Trump, and it is not normal politics," she said at a stop Saturday in Oxnard. "This is something much, much more dangerous."
When Dickerson challenged Trump on CBS to explain what Curiel's Mexican parents had to do with his ability to be impartial in the fraud case, Trump said, "Excuse me, I want to build a wall."
"We have to stop being so politically correct in this country," Trump said. "And we need a little more common sense."
In another interview that ran Sunday, CNN anchor Jake Tapper asked Trump, "If you are saying he can't do his job because of his race, is that not the definition of racism?"
"No, I don't think so at all," Trump said.
"He is a Mexican," Trump added. "We are building a wall between here and Mexico."