Things heated up on Sunday in the spat between Republican party presidential nominee Donald Trump and the parents of a slain Muslim US Army officer who was decorated posthumously for his sacrifice to save his troops in the Iraq war. But one important group of people was notably absent from Trump's side: top Republican leaders. The GOP brass either stayed quiet or issued statements defending the family of Captain Humayun Khan, without even mentioning the name of their own presidential candidate.

Trump had been getting got a lot of flak for his response to Khizr Khan's speech at the Democratic National Convention on Thursday night. Khan, born in Pakistan, is a lawyer and a US citizen, and also a Muslim. His son was killed by a car bomb in Iraq in 2004, after he ordered his unit to stand back and went to check the vehicle himself.

Khan spoke slowly and deliberately about being Muslim and being American, using strong words that questioned Trump's integrity and patriotism, and moving many in the Philadelphia audience to tears. At the heart of the Trump-Khan debacle is the Republican nominee's controversial proposal – a cornerstone of his campaign – to ban Muslims from traveling to the US.

Trump claimed in a tweet that he was "viciously attacked" by Khan.

He responded to Khan's speech with a series of comments that were mainly directed at Ghazala Khan, who stood next to her husband silently when he spoke at the DNC. "If you look at his wife, she was standing there," Trump said on ABC News on Saturday. "She had nothing to say. She probably, maybe, she wasn't allowed to have anything to say. You tell me." His comments have been roundly denounced as ignorant and racist.

In an op-ed for the Washington Post and in an emotional interview with MSNBC on Saturday, Ghazala Khan made it quite clear that she was not being silenced. She explained she didn't speak at the DNC because she continues to be overwhelmed with grief over her son's death. Khizr Khan also spoke about why he needed to have his wife at his side during the speech.

"Her being there was the strength that I could hold my composure," he said. "I am much weaker than she is in such matters."

Speaking on CNN on Sunday, Khizr was incensed at the treatment of his wife, and said Trump has "a black soul."

Later in the day, Senate majority leader Mitch McConnell released a statement defending the Khans, without even mentioning Trump's name.

"Captain Khan was an American hero, and like all Americans I'm grateful for the sacrifices that selfless young men like Captain Khan and their families have made in the war on terror," McConnell's statement said. "All Americans should value the patriotic service of the patriots who volunteer to selflessly defend us in the armed services. As as I have long made clear, I agree with the Khans and families across the country that a travel ban on all members of a religion is simply contrary to American values." The last part is a direct dig at Trump's often-repeated claim that he would ban Muslims from entering the US.

House Speaker Paul Ryan, the other top Republican in Congress, tweeted a strongly-worded statement on the issue – again, without mentioning Trump's name.

A religious test for entering our country is not reflective of America's fundamental values. I reject it. — Paul Ryan (@SpeakerRyan)July 31, 2016

Another Republican heavyweight in the Senate, South Carolina's Lindsey Graham, told the New York Times that Trump's swipes at the Khan family were unacceptable. "There used to be some things that were sacred in American politics, that you don't do, like criticizing the parents of a fallen soldier, even if they criticize you," Graham said. "If you're going to be leader of the free world, you have to be able to accept criticism, and Mr. Trump can't."

Ohio governor John Kasich, who fought Trump in the presidential primaries, also chimed in, and also omitted the name of his own party's standard-bearer. "There's only one way to talk about Gold Star parents," Kasich wrote. "With honor and respect. Capt. Khan is a hero." Gold Stars are awarded to the families of service members killed in combat.