Senator Lindsey Graham, Republican of South Carolina, said on Sunday that Mr. Trump had crossed another inviolable line. Like his comments about Judge Curiel, Mr. Graham said, Mr. Trump’s jabs at Mr. and Ms. Khan were unacceptable. “This is going to a place where we’ve never gone before, to push back against the families of the fallen,” he said
Democratic leaders and candidates for Congress began over the weekend to call on Republicans to disavow Mr. Trump. And the top two Republicans in Congress, House Speaker Paul D. Ryan and Senator Mitch McConnell, the majority leader, signaled their strong disagreement with Mr. Trump, but stopped short of condemning him in blunt terms.
Hillary Clinton, the Democratic presidential nominee, sternly reprimanded Mr. Trump on Sunday morning, saying at a church in Cleveland that he had answered the Khan family’s sacrifice with disrespect for them and for American traditions of religious tolerance.
“Mr. Khan paid the ultimate sacrifice in his family, didn’t he?” Mrs. Clinton said. “And what has he heard from Donald Trump? Nothing but insults, degrading comments about Muslims, a total misunderstanding of what made our country great.”
Mrs. Clinton chastised Mr. Trump again on Sunday in Ashland, Ohio, calling his comments part of a disturbing pattern. “He called Mexicans rapists and criminals,” Mrs. Clinton said. “He said a federal judge was unqualified because he had Mexican heritage — someone born in the neighboring state of Indiana. He’s called women pigs. He’s mocked a reporter with a disability.”
Mr. and Ms. Khan stiffened their denunciation of Mr. Trump on Sunday, saying that he lacked the moral character and empathy to be president. Mr. Khan, who addressed the Democratic National Convention on Thursday, said on “Meet the Press” on NBC that Mr. Trump had shown disrespect to his wife, and he accused Mr. Trump of running a campaign “of hatred, of derision, of dividing us.”
In a direct appeal to voters inclined to support Mr. Trump, Mr. Khan pleaded with them to reject his brand of politics.
Addressing “patriotic Americans that would probably vote for Donald Trump,” Mr. Khan said, “I appeal to them not to vote for hatred, not to vote for fear-mongering. Vote for unity. Vote for the goodness of this country.”
And Ms. Khan, in an opinion article published in The Washington Post, rebuked Mr. Trump for suggesting earlier in the weekend that she had not been permitted to speak at the Democratic convention. Ms. Khan said she did not speak because she did not believe she could remain composed while talking about her son.
“All the world, all America, felt my pain. I am a Gold Star mother. Whoever saw me felt me in their heart,” Ms. Khan wrote, using the term for surviving family members of those killed in war. “Donald Trump has children whom he loves. Does he really need to wonder why I did not speak?”
Ms. Khan said Mr. Trump was “ignorant” of Islam and criticized him for offering his business career as evidence that he had sacrificed for his country. “Donald Trump said he has made a lot of sacrifices,” Ms. Khan said. “He doesn’t know what the word sacrifice means.”
It is too soon to say how severe the damage to Mr. Trump might be, but the clash has already entangled him in a self-destructive, dayslong argument with sympathetic accusers who are portraying him as a person of unredeemable callousness. Still, he has proved remarkably resilient, getting past controversies that might have sunk other candidates.
Several prominent Republicans have condemned Mr. Trump’s treatment of the Khans, calling his behavior outside the bounds of political discourse. But Republican congressional leaders responded cautiously to Mr. Trump. Mr. Ryan and Mr. McConnell released statements stressing their admiration for the Khan family; Mr. McConnell called Capt. Humayun Khan an “American hero.” And both said they firmly opposed banning Muslim immigration, though neither mentioned Mr. Trump, whom they have endorsed, by name.
“Many Muslim Americans have served valiantly in our military, and made the ultimate sacrifice. Captain Khan was one such brave example,” Mr. Ryan said. “His sacrifice — and that of Khizr and Ghazala Khan — should always be honored. Period.”
Mr. Trump’s clash with the Khan family threatens to unwind any progress he may have made at moderating his campaign and rallying his party at the outset of the general election. He has sought to play down his proposal for banning Muslim immigration, focusing on blocking immigration from specific countries instead, but has never disavowed the idea of a religious test. And he has not apologized to the Khans for his comments about Ms. Khan.
Those comments have deeply unsettled many leading Republicans. Jeb Bush, the former governor of Florida, and John Kasich, the governor of Ohio, have forcefully expressed disapproval. A spokesman for former President George W. Bush declined to comment directly on Mr. Trump’s behavior, but suggested Mr. Bush takes a different view.
“President Bush remains deeply grateful for the sacrifice of all Gold Star families, as we all should be. He thinks about them and prays for them each and every day,” said the spokesman, Freddy Ford.
Other Republicans went even further in chiding Mr. Trump. Senator Kelly Ayotte of New Hampshire, who is seeking re-election, said the Khans deserved the utmost respect: “I am appalled that Donald Trump would disparage them and that he had the gall to compare his own sacrifices to those of a Gold Star family.”
He added, “The problem is, ‘unacceptable’ doesn’t even begin to describe it.”
Representative Mike Coffman of Colorado, a Republican who served in combat as a Marine and now represents a crucial swing district in the Denver suburbs, said Mr. Trump had disrespected American troops. “Having served in Iraq, I’m deeply offended when Donald Trump fails to honor the sacrifices of all of our brave soldiers who were lost in that war,” Mr. Coffman said.
The pressure on Mr. Trump and other Republicans is unlikely to relent soon. But so far he has flailed and faltered in response.
He first criticized Ms. Khan for not speaking alongside her husband, implying that she had been prohibited from doing so. Facing mounting criticism from Democrats and Republicans, he released a follow-up statement on Saturday night, describing the Khans’ deceased son as a hero, but insisting that Mr. Khan had “no right” to criticize him the way he did in Philadelphia. He made a third attempt to deflect the Khans’ criticism on Sunday, writing on Twitter that the real issue at stake in the election was terrorism.
The Republican vice-presidential nominee, Gov. Mike Pence of Indiana, appears to be in a particularly awkward position in the uproar. His son is a Marine, a fact he mentions frequently. Mr. Pence’s ability to navigate a racially charged argument between Mr. Trump and a Gold Star family is emerging as his first difficult test as Mr. Trump’s running mate.
For most of the weekend, Mr. Pence was silent. His aides referred inquiries to Mr. Trump’s staff, and his lone public comment was a Twitter post about getting his hair cut in Indianapolis.
Late Sunday, Mr. Pence issued a statement sidestepping Mr. Trump’s criticism of the Khans. He expressed appreciation for the family’s sacrifice and reiterated his support for blocking immigration “from countries that have been compromised by terrorism.”