Madeline Carroll, 12, is winning critical praise for her role as Molly in Swing Vote, with Kevin Costner.

Disney / Ben Glass

BOSTON Madeline Carroll, who is winning praise from the critics for her first starring role, as Kevin Costner’s determined and wise daughter in Swing Vote, is poised and confident during an early morning interview at a posh hotel. She seems older and wiser than her 12 years.

Her long hair, and an almost floor-length cotton jacket worn over a yellow T-shirt and floor-length granny skirt because of the hotel’s chilly air conditioning, enhance that sense.

But then Madeline gets caught up in trying to make a crystal goblet “sing” by rubbing her finger around its rim and one thinks: Yeah, she really is a kid.

Madeline, who has been appearing in print ads, TV commercials and small movie roles since she was 3, takes great joy when a studio publicist shows her that by holding the base of the goblet, the sound comes more easily.

“Yeah, I can do it!” she says with a gleeful sense of accomplishment as a piercing whine comes from the top of the glass.

Although some have already favorably compared Madeline to young star actresses Abigail Breslin and Dakota Fanning, she comes across as unpretentious and down to earth. In fact, although there was a tutor for her on the New Mexico set of Swing Vote when production lingered from late last summer into September, she says she attends a public school in suburban Los Angeles and will be in the seventh grade there when school begins in a few weeks.

Her friends, she says, think her working with the likes of Academy Award-winner Costner, Dennis Hopper and Kelsey Grammer in Swing Vote is “cool. They don’t get all jealous. Some people get cranky, but they’re really nice. My friends are awesome.

“I guess they like that I do it, but I don’t think they’re into [acting] themselves.”

In Swing Vote, Madeline plays Molly, the savvy and responsible daughter of a slacker father, played by Costner. In a very real sense, she has become the adult in this family, prodding her father to get up and go to work, registering him to vote for the presidential election and then pushing him to meet her at the polling place.

She said Molly’s wise-beyond-her-years life was the result of her “knowing since she was a little girl that she has to take care of her Dad because he has . . . issues.”

Critics have praised a couple of the film’s big emotional scenes, in which Madeline’s eyes well up with tears. “I would think about my family,” she says when asked about how difficult those scenes were to pull off. “My dog passed away just before we started the movie, so that just helped me cry.

“But it’s not about crying, really, but about what’s happening to [Molly]. When I read the script, it made me cry when I had to get into her shoes and understand how she was feeling.”

Madeline is the only girl in her family; she has three brothers, ages 6, 10 and 15, and her 10-year-old brother has done a bit of work in commercials. “But we don’t force him,” she says, sounding a little like the motherly Molly. Her own mother, she says, is a homemaker and her father is a contractor.

Madeline first got in front of a camera when she was 3, appearing in print ads for department stores.

“Then, when I was like 5 and was in a nail shop with my aunt, Wendy Green came along and offered to be my agent.”

Green “discovered” the little girl and before long Madeline was appearing in TV commercials and, eventually, movies.

Although she plays the “parent” in her scenes with Costner in Swing Vote, she says that at home she never tries to boss her own parents around.

“No,” she says with a laugh, “I would get killed.”

mjanuson@projo.com