Marko Djurica / Reuters John McCain is emerging as the most prominent Republican with the gall to publicly reject Donald Trump.

WASHINGTON ― Khizr Khan, the Gold Star father and Muslim American who’s emerged as one of Donald Trump’s most compelling critics, has for weeks been calling on Republicans to pull their support for the presidential nominee over his proposal to ban Muslims from entering the United States.

But on Tuesday he appealed directly to one GOP lawmaker in particular: his hero, Sen. John McCain (R-Ariz.).

“I implore Senator McCain ... I continue to implore all of the good Republicans who either support or are going to vote for their party’s candidate, this will be a historic moment in the Republican Party,” Khan said in an interview with Cronkite News, the news division of Arizona PBS.

“If you publicly rebuked him, you will look back and you will stand tall in front of the nation and you will say you were not for this, we were for [a] better America,” he said.

Khan, whose son, Humayun, was a U.S. Army captain killed in Iraq while protecting his troops, is a big fan of McCain’s. He called the Arizona senator “my and my family’s hero” and said one of the last talks he had with his son was about McCain’s book, Why Courage Matters.

How can McCain say no to this guy?

McCain campaign spokeswoman Lorna Romero declined to comment on whether the senator would un-endorse Trump. Instead, she pointed to a lengthy statement he put out last week praising the Khan family and dismissing Trump’s proposed ban.

“He has suggested that the likes of their son should not be allowed in the United States ― to say nothing of entering its service,” McCain said in his statement. “I cannot emphasize enough how deeply I disagree with Mr. Trump’s statement. I hope Americans understand that the remarks do not represent the views of our Republican Party, its officers, or candidates.”

He’s still endorsing Trump for president, though.

It’s not the first time Trump’s critics have singled out McCain as the guy they think has the gall to publicly reject his party’s presidential nominee. Military veterans from around the country flew into Washington, D.C., last week to deliver a petition with 100,000 signatures to McCain’s office, urging him and other GOP leaders to yank their support for Trump.

Rep. Ann Kirkpatrick (D-Ariz.), who is running for McCain's Senate seat, knocked the senator for standing by Trump no matter what he says.

“John McCain has changed so much after 33 years in Washington that he’s now willing to ignore a Gold Star father and continue clinging to Donald Trump because he believes it will help save his political career," she said in a statement. "McCain’s failure to answer Mr. Khan proves the straight talk is gone and it’s McCain and Trump first, not country first."

McCain is currently leading Kirkpatrick by about 5 percentage points, according to HuffPost Pollster.

Editor’s note: Donald Trump regularly incites political violence and is a serial liar, rampant xenophobe, racist, misogynist and birther who has repeatedly pledged to ban all Muslims ― 1.6 billion members of an entire religion ― from entering the U.S.

This article has been updated with a comment from Ann Kirkpatrick.