She plays scheming breakout country sensation Juliette Barnes, who's locked in a love-hate rivalry with country music queen Rayna Jaymes (co-star Connie Britton), whose long reign is threatened by Juliette's rise.
Panettiere nails her role, displaying a deft blend of rapaciousness and vulnerability, not to mention impressive pipes.
In the process, she has pulled off two overarching victories. She's left behind her past signature role, the indestructible Cheerleader in the sci-fi drama "Heroes" -- a character that could have tied her down forever.
Even more remarkably: At 24, she's crossed that treacherous Rubicon that few young actors navigate, from adolescence to the far shore of adulthood.
"'Nashville' was perfect timing with the perfect character," she said. "Juliette is so not the good girl that I played on 'Heroes,' but she has to put on the facade as a good girl to get what she wants.
"Juliette is tough, but when she cries, she means it: She's a very damaged young woman running from a dark past. How much more perfect could I ask for?"
Sure, Juliette is the show's resident villain, "but you get to see her inner workings, what she goes through," Panettiere said.
"It's great to show the audience Juliette's terrible behavior, and then show where that behavior came from: not from a place of malice, but of pain," she said.
"A lot of what I've drawn from is my own personal experience," she said. "I grew up in the entertainment industry, in the spotlight, and have had to deal with some of the same struggles.
"In this business, there are so many doors wide open to walk through and it looks like the normal thing to do."
"The difference is, I've always had people around me to yank me back before I went too far," she said.
Panettiere's mother was an actress, her father a New York City firefighter, and she made her screen debut as an infant in a Playskool toys commercial.
Since then she's never stopped acting, nor did she imagine doing anything else. But after "Heroes" ended in 2010, she faced a dry spell before "Nashville" came along.
"It hit me like a ton of bricks," she said."There is a genuine possibility that no one will ever take another chance on me. That was an important gap between 'Heroes' and this show, a huge transition to make gracefully. I don't know how gracefully I did it, but somehow I did."
Callie Khouri, "Nashville" creator and executive producer, said she was unconcerned while casting her new series that Panettiere might still be the Cheerleader in viewers' minds.
"When she stood in front of the camera as Juliette, I saw the character that I needed, not the one she'd already done," said Khouri by phone from Nashville, marveling at her range:
"She can go from being the worst little brat in the world to absolutely breaking your heart."
"Nashville" airs at 10 p.m. Wednesdays on ABC.
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