The 3-year-old daughter of Republican presidential candidate Rick Santorum was admitted to Children's Hospital of Philadelphia Saturday and the candidate canceled his Sunday-morning campaign events to be at her side.

Santorum campaign spokesman Hogan Gidley said Saturday night the former Pennsylvania senator and his wife, Karen, were with Bella at the hospital. Gidley said Santorum planned to return to campaigning as soon as possible in Florida, where the Republican primary is Tuesday.

Bella has Trisomy 18, a genetic condition caused by a third copy of material from chromosome 18 instead of two, leading to a wide array of physical and mental problems.

She was not expected to survive until her first birthday - half of infants with Trisomy 18 do not survive their first week, according the National Institutes of Health. Some children have lived to their teenage years, but with significant medical and developmental issues.

The Santorums have been frequent visitors to Children's Hospital with their daughter, and concerns over her health have canceled previous Santorum campaign events.

During his campaign, Santorum and his wife have spoken openly about the challenges and rewards of raising a child with such a condition.

The Santorums have six other children; they lost a baby boy, Gabriel, shortly after his birth in 1996. Bella was born in 2008; two years later, Santorum wrote about her in an Inquirer column.

"All children are a gift that comes with no guarantees," he wrote. "While Bella's life may not be long, and though she requires our constant care, she is worth every tear."

Bella, whose full name is Isabella Maria Santorum, has become a symbol of the candidate's pro-life stance, as he claimed that most infants diagnosed in the womb with Trisomy 18 are aborted.

"I have a little girl who's 3 1/2 years old," he told Christian conservatives in Iowa before winning that leadoff contest.

"I don't know whether her life is going to be measured - it's always been measured - in days and weeks. Yet here I am . . . because I feel like I wouldn't be a good dad if I wasn't out here fighting for a country that would see the dignity in her and every other child."

When voters ask him about her, he calls the decision to campaign painful but says he does it for all special-needs families.

"You think she's fine, and then one cold and she's this close to dying," he told the Washington Post last year in an interview.

In October, he missed one of Bella's surgeries to participate in a debate, and he told the audience he planned to take an all-night flight home from Las Vegas to be with her.

"I look at the simplicity and love she emits," Santorum said in a Web video his campaign released after his scheduling drew questions, "and it's clear to me we're the disabled ones."

Santorum has largely kept his daughter off his campaign schedules, preferring her to stay home with her mother. But Bella did join him for a few days around Iowa's straw poll in August, and she joined her family in Charleston, S.C., on the day of that state's primary. She didn't join her six siblings for the public speech. She stayed backstage.

Santorum had been scheduled to appear on NBC's Meet the Press Sunday and to attend church in Miami. He was in the Philadelphia area as recently as Friday night to attend a campaign fund-raiser in Chester County.