MANCHESTER, N.H. -- The father of a Muslim U.S. Army soldier killed in Iraq rebuked Republican presidential nominee Donald Trump on Sunday as an embarrassment to the United States, as a somber and reflective Hillary Clinton pledged to work for “healing and reconciliation” after the election.

Khizr Khan, making a campaign trail debut after coming to prominence at the Democratic National Convention, retold the story of his son Humayun Khan. The younger Khan died in 2004 when he told his men to stay back as he approached a suspicious car. He was the only American to die in the explosion.

Khan waved and raised a fist in the air before introducing Clinton, whom he praised for her experience and temperament. He told a supportive crowd that after he spoke at the convention and Trump attacked him as a Democratic shill, he and his family had received thousands of letters and messages of support.

“This election will decide the future of America and the future of the world,” Khan said. “On one hand, we have Donald Trump and his policies of hate, exclusion, intimidation and division,” he said. “On the other hand, we have Hillary Rodham Clinton and her lifelong public service to the country.”

Khan is an unlikely political star, a middle-aged Pakistani-born lawyer, but his convention speech is one of the most memorable moments of the campaign. It also was a turning point, with Trump's angry reaction setting off weeks of disarray on the Republican side.

Trump recovered politically, but Clinton's campaign has sought to keep the powerful story of Khan and Trump's willingness to attack the dead soldier's parents at the center of the political contest.

Clinton gave a subdued version of her stump speech focused largely on the threat she said Trump poses to American values and national security.

“In a race that has been marked by ugly suspicions and insults and attacks of all kinds ... Mr. Khan, I think, reminded all of us that we are Americans,” she said. “His son was an American who gave his life for our country. We cherish the Constitution, and we will defend it.”

New Hampshire is one of the battleground states where a testimonial ad featuring Khan is playing. The ad, released last month, shows Khan walking through his home, looking at his son's pictures and military honors. It closes with a tearful Khan addressing Trump directly, as he did at the convention.

“I want to ask Mr. Trump: Would my son have a place in your America?” he asks.

Before Khan took the stage, musician James Taylor performed several songs with an election theme, including “You've Got a friend” and "(You Are My) Only One,” which he dedicated to Clinton.

It was Clinton's second celebrity serenade of the day — R&B singer Bebe Winans sang to her at a church service in Philadelphia — and it was part of a star-spangled final few days that put Democrats' ties to the entertainment world on display.

Katy Perry sang on Saturday night in Philadelphia, and Jay-Z and Beyoncé performed Friday night in Cleveland. Clinton's campaign announced that Bruce Springsteen will perform at a closing rally Monday night at which President Obama and first lady Michelle Obama will join Clinton and her husband, former president Bill Clinton.