kelly clarkson II people.com

Kelly Clarkson Reveals Who Her Husband (& Blake Shelton's Manager!) Is Rooting for on The Voice

Though the two are longtime friends, they mean business when it comes to competing against each other on the singing competition series as coaches.

“Make no mistake, Kelly is my friend,” Shelton, 41, tells PEOPLE exclusively of the Voice newbie, 35. “But when she’s on this show, she is my enemy.”

Clarkson, who loves that she’s “a threat” to him, first appeared on the show as Shelton’s celebrity advisor during season two. Her husband, Brandon Blackstock, is also Shelton’s manager — but she says he’s not taking sides.

“He’s like Switzerland,” she says. “I always do say though that at least I put out — so unless he’s doing something I don’t know about, I should win!”

Shelton adds, “If I fire Brandon, it’s one thing. If she fires him, it’s going to be real bad. He knows who to suck up to.”

While he might not entirely have Blackstock behind him, Shelton definitely has a fan in Clarkson’s daughter, River Rose, 3.

“My daughter loves Blake,” Clarkson says. “He has this gravitational pull. I’ve even seen him with [his girlfriend] Gwen [Stefani]‘s son Apollo and her kids, and he’s like this tree that they all climb on.”

When it comes to taking advice from Shelton — who has won the show a record six times — Clarkson says she looks to his actions as inspiration instead.

“He makes jokes but he really does help people after the show, and I’d like to do that as well,” she says before adding, “But he will mess with me left and right!”