It seems that more popular musicians are backing a presidential candidate than ever before. I don't know how important that is, since musicians are neither smarter nor dumber than any other supporters -- but I suppose it could sway some fans of these musicians who don't pay a lot of attention to politics.
Here is The Guardian's count of which musicians are backing which candidates for the 2016 presidential campaign:
Kanye West, Beyoncé, Pharrell Williams, Katie Perry, Christina Aguilera, Burt Bacharach, Tony Bennett, Jon Bon Jovi, Mariah Carey, Cher, Kelly Clarkson, Ellie Goulding, Ice-T, Ja Rule, Elton John, Quincy Jones, Lady Gaga, Jennifer Lopez, Ricky Martin, Janelle Monae, Morrissey, Snoop Dogg, 50 Cent, Sting, Barbra Streisand, James Taylor, Usher, will.i.am, Stevie Wonder
Killer Mike, Lil B, Lou Barlow of Dinosaur Jr, Jello Biafra of the Dead Kennedys, Belinda Carlisle of the Go-Go’s, Jon Fishman of Phish, Billy Gould of Faith No More, Chris Shiflett of the Foo Fighters, Maureen Herman of Babes in Toyland and Thurston Moore of Sonic Youth, David Crosby, Mike Watt of the Stooges, Donovan (Mellow Yellow guy, British not American), Red Hot Chili Peppers, Vampire Weekend
Johnny Van Zant, the lead singer of Lynyrd Skynyrd
Kenneth “Babyface” Edmonds
The Guardian didn't find any popular musicians supporting the other candidates.