Katy Perry, latest in string of stars to sing Clinton's praises

Three days before the election, pop singer Katy Perry gave a Philadelphia performance Saturday hoping to boost the Democrat's momentum.

Superstar Jennifer Lopez headlined a recent Miami concert hoping to rally voters for Clinton, and Friday night the US secret service said 10,000 hip hop fans turned out in Cleveland, Ohio for a free star-studded rally concert headlined by power couple Beyonce and Jay Z.

"All the campaigning in the world doesn't mean anything if people don't vote," Clinton said, shortly before presenting her fervent supporter Perry, who already stumped last year for the Democratic presidential candidate.

"When you get knocked down, which everybody does, what matters is get back up," Clinton said.

"Stand up for what you believe. Know the power of your own voice."

The 32-year-old Perry then performed her hit "Roar," a standard on the White House hopeful's official playlist.

Celebrity performances on the campaign trail are not unique to Clinton: Barack Obama attracted some 80,000 people to a 2008 Bruce Springsteen concert in Cleveland just days before Americans headed to the polls.

Despite strict controls at the door, the smell of marijuana wafted throughout the stands at the first sounds of Jay Z. Several other top rappers appeared at the event in an attempt to woo young voters.

The artists worked to instill a sense of urgency in their fans just days before the vote. Beyonce voiced pride at having had a black president for the past eight years, and called for the US to elect a woman this time.

The Clinton campaign's concerts are aimed at attracting voters who would rather spend their weekend nights anywhere but an election rally.

"I heard on the radio 'Katy Perry live,'" said Josh Burns, a 24-year-old architect. "I didn't know it was a Hillary thing."

"It's a good tactic, I like it."

But was the young voter convinced?

"It's good that artists are supporting Hillary," he said. "It makes you realize how worried they might be."