Her chin quivers and her eyes brim with tears. At one point she becomes so choked up that she is unable to keep singing even as the playback continues and the cameras roll.

With the understated yet emotion-wracked video for Sugarland's current single "Stay" - a devastating ballad sung from the point of view of the "other woman" - singer Jennifer Nettles has ceased being Nashville's best-kept secret and is poised for breakout stardom.

After watching the video, YouTube commenters are writing those familiar missives that begin, "I don't usually like country music but ..."

Last month the American Music Awards invited Nettles and Sugarland partner Kristian Bush to join Beyoncé to put a Southern spin on the R&B diva's "Irreplaceable." And immediate reverberations were felt following a powerhouse performance of "Stay" at the Country Music Association Awards, also last month, that brought Music City to its feet.

(Sugarland also won the best vocal duo award, breaking the ironclad grip of Brooks & Dunn on that particular honor. This was thanks in part to the trio's becoming a duo with the reportedly amicable 2006 departure of cosongwriter Kristen Hall.)

MySpace friend requests skyrocketed, as did YouTube video views; and sales of

Enjoy the Ride

, Sugarland's already-platinum 2006 sophomore album, enjoyed a 112 percent week-to-week increase, according to Nielsen Soundscan.

Released in mid-September as the fourth single from

Ride

, "Stay" was an instant success, fueled in large part by that intensely vulnerable video that recalls Sinead O'Connor's similarly teary-eyed "Nothing Compares 2 U" in that it is shot mainly in long, stark close-ups that eschew corny narrative, quick cuts, or glitz of any kind. There is a rawness to it that cuts through the veneer applied to almost all current country and pop music. It feels authentic.

(Nettles, who was recently divorced, told the Tennesseean newspaper that she relates to the loss in the song, but that its situation differs from her own experience.)

It quickly became the most-viewed clip on CMT.

It's easy to see why, and obvious to anyone who has seen Sugarland work the opening-act and award-show circuit for the last three years.

From the AMAs to the CMAs to the Grammys, where Sugarland was nominated for best new artist last year, Nettles, with the help of Bush, more than holds her own. Even standing next to a Beyoncé. Add her spunky stage presence and Nettles' gifts are abundantly clear.

If some of Sugarland's material, written mainly by Nettles and Bush, occasionally hews a little too closely to the current Nashville factory settings, there is no disputing that voice. With a deep twang, gale-force power, and an acute sense of where soul music and country intersect, Nettles takes her cues equally from Tammy Wynette, Dusty Springfield and Janis Joplin, while rarely overplaying any of those influences.

And in the case of "Stay," which she wrote solo, she has conceived a song that covers classic country music territory - cheatin' hearts - in a way that resonates with contemporary listeners without a lot of melodramatic, or melismatic, fuss.

Few female-fronted bands have managed to have staying power in country music. Sugarland just may be the group that changes that. With the success of "Stay" a whole new group of listeners may get a sweet tooth, and that is nothing to cry about.

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