Donald Trump finds himself increasingly isolated over his persistent attacks on the ethnicity of a Hispanic federal judge.

As Republicans moved en masse to disassociate themselves from the remarks, Democrats worked to tie the entire Republican Party to them.

The attacks on US District Judge Gonzalo Curiel - who Trump says is unfit to hear two lawsuits against Trump University because of his "Mexican heritage" - threaten to erode the real estate mogul's tepid support within the Republican establishment, which has cautiously fallen behind him in recent weeks.

GOP legislators and strategists face uncomfortable questions about how they can support Trump without also tacitly endorsing his criticism of Curiel and his remarks that a Muslim judge might also be questionable.


Some Republican legislators arriving on Capitol Hill scurried from reporters to avoid answering questions about the remarks; others condemned the comments as wrong while saying they would still support Trump as the Republican nominee.

One of the strongest criticisms came from Senator Susan Collins of Maine, who has said that she plans to support the presumptive GOP nominee. "His statement that Judge Curiel could not rule fairly because of his Mexican heritage does not represent our American values," Collins said. "Mr Trump's comments demonstrate both a lack of respect for the judicial system and the principle of separation of powers."

The episode has distracted from the Trump campaign's efforts to unite the party ahead of a competitive general election bid against Hillary Clinton, who locked up the Democratic nomination today, according to an AP count of delegates. Democrats hope to use his comments - the latest in a series of attacks and proposals that have infuriated Hispanic voters - to paint the entire Republican Party as out of touch with minorities.

Clinton said during a campaign appearance in suburban Los Angeles that his remarks are contrary to American values.

"I'm waiting for him to say, because of the bigoted things he has said about women, that a woman judge couldn't fairly preside over a case," Clinton said. "By the time he's finished, nobody is going to be left in this country that he is going to have exempted from insults. We need to stop this divisiveness, this bullying and bigotry."

Republican sources said there have been multiple efforts in recent days to convey displeasure to Trump and his senior advisers, urging Trump to pull back on his assault. The entreaties have included major GOP donors and Republican National Committee chair Reince Priebus.

Trump has resisted those recommendations. Instead, he has responded the way he often does when challenged: by digging in harder than ever. "If somebody else were there, this would have been thrown out on summary judgment," Trump said about Curiel in a Fox News interview today, adding: "All I'm trying to do is figure out why I'm being treated so unfairly by a judge."