So who do you want answering the phone at 3am? For Casey Knowles, it's got to be Barack Obama.

Casey is the little girl shown asleep in the controversial Hillary Clinton advert that aired in Texas before last week's primary, playing on fears about Mr Obama's relative lack of experience in foreign policy matters.

The advert shows the exterior of a Colonial-style home and old stock footage of Knowles sleeping in bed. A narrator describes a phone ringing in the White House: “It’s 3am and your children are safely asleep. Who do you want answering the phone?”

Mrs Clinton won the Texas primary by a 51-47 per cent margin.

Casey was just 8 at the time the video, bought by the Clinton campaign from Getty Images as stock footage, was shot, originally for a rail company advert.

Ms Knowles is now almost 18 and said yesterday that she had not seen the advert until it was lampooned by a TV satire show. Her brother noticed it was her, and the family replayed the commercial on their digital recorder to be sure.

"They were parodying this ad, kind of poking fun at it,” she told the ABC network. “My brother was like, ’Is that Casey?’ And we just erupted. Sure enough, it’s me.”

But she is not too happy about the advert itself. “What I don’t like about the ad is its fear-mongering,” she said. “I think it’s a cheap hit to take. I really prefer Obama’s message of looking forward to a bright future.”

Ms Knowles, a high school senior in Washington state, has been campaigning for Mr Obama and attended his rally at Seattle’s KeyArena on February 8, crying and trembling after shaking his hand.

The next day, she was a Democratic precinct captain for the state’s caucuses and she could yet be chosen to go to the national convention – although she will end up voting for whichever candidate the party chooses in November's election.

Before then Ms Knowles she might feature in another advert. She has already suggested to the Obama campaign that she team up with the candidate for an anti-Hillary ad. “They thought that was really funny. They actually might take me up on it,” she said.

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