One of Donald Trump's most effective antagonizers has emerged again in the final weeks of the presidential campaign to deal what might be a final blow to his candidacy.

In an emotionally raw 60-second ad, Gold Star father Khizr Khan walks through the Virginia home he shares with his wife, Ghazala, reliving the ultimate sacrifice his son, Army Capt. Humayun Khan, made in the line of duty.

Humayun Khan was 27 years old when he was killed while rushing toward a suicide bomber who was attempting to approach his unit in 2004 in Iraq.

“He was a Muslim American,” Khizr Khan says of his son in the ad, his voice cracking with emotion. “I want to ask Mr. Trump, ‘Would my son have a place in your America?’ ”

Trump's feud with the Khan family was one of the most explosive and damaging moments for his candidacy, and it prompted widespread criticism as Trump seemed eager to defy political norms against criticizing the families of fallen soldiers.

Khan appeared with his wife at the Democratic National Convention in July, and in his speech he said Trump had “sacrificed nothing” and questioned whether he had read the Constitution.

“If it was up to Donald Trump, [Humayun] never would have been in America,” Khan said in his DNC speech. “Donald Trump consistently smears the character of Muslims. He disrespects other minorities, women, judges, even his own party leadership. He vows to build walls and ban us from this country.”

Trump fired back in a war of words that lasted days, prompting sharp criticism from leaders in both parties.

“I think I’ve made a lot of sacrifices. I work very, very hard,” Trump said in an interview with ABC News.

In that same interview, he commented on Ghazala Khan, suggesting that she wasn't permitted to speak.

“His wife … if you look at his wife, she was standing there. She had nothing to say,” Trump added. “Maybe she wasn't allowed to have anything to say; you tell me.”

In the weeks after, Trump's numbers fell sharply in the polls.

With just 18 days left until the election, the new ad featuring the Khans reprises Trump's feud with the family, as Clinton makes her closing argument to voters. It will air in Florida, Iowa, Nevada, New Hampshire, North Carolina, Ohio and Pennsylvania.

It comes at a time when Trump is falling further behind Clinton in key battleground state polls and nationally. He has lashed out against leaders in his own party, and Republicans are increasingly alarmed by the prospect that Trump could be on track for a landslide defeat.