Elton John, who has sold records and filled arenas for four decades, played a benefit concert for Clinton at Radio City Music Hall.
"I've always been a Hillary supporter," John, 61, said before launching into his 1970 breakthrough hits, "Your Song" and "Border Song." "There is no one more qualified to lead America."
The English singer, composer and pianist added: "I'm amazed by the misogynistic attitudes of some of the people in this country. And I say to hell with them .... I love you Hillary, I'll be there for you."
Preceding John on stage were Clinton, her husband, former President Clinton, and their daughter, Chelsea.
Hillary Clinton struck a defiant, underdog note in describing her battle against Sen. Barack Obama of Illinois.
"What I want you to know is I'm still standing, and I believe this country is worth fighting for," the New York senator said, playing off the title of one of John's hits. "So we're taking our campaign to Pennsylvania and all the states that haven't voted." Pennsylvania votes April 22.
The Clintons have hobnobbed with Hollywood and music industry figures for years. In 1998, John performed at a White House State Dinner the couple hosted for then-British Prime Minister Tony Blair.
Last October, Clinton celebrated her 60th birthday with a fundraiser at New York's Beacon Theater that featured actor Billy Crystal and musicians Elvis Costello and the Wallflowers. It netted more than $1.5 million for her presidential effort.