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ARCADIA, Fla. - Rick Santorum will not appear at any of his Florida campaign stops today, instead staying with his family and youngest daughter Isabella, who was admitted into a Philadelphia hospital Saturday evening.

"Due to the heath of his youngest daughter Bella, Rick Santorum will remain with his family today," Santorum campaign spokesman Hogan Gidley said in a statement today. "However, the campaign will resume the following Florida schedule using surrogates. Rick himself intends to return to Florida and resume the campaign schedule as soon as is possible."

The 3-year-old, whom the family calls Bella or Boo, suffers from the rare and serious genetic condition Trisomy 18, which kills about 90 percent of children before or during birth. She is at Children's Hospital of Philadelphia, where she is regularly treated.

Santorum's eldest daughter, Elizabeth, 20, will appear at a Sarasota rally this afternoon in his place, along with members of the Duggar family from the TLC show "19 Kids and Counting." The family has campaigned with Santorum in Iowa, South Carolina, and now Florida. The family will also appear at a Lincoln Day Dinner in Punta Gorda, where Santorum was supposed to speak this afternoon.

The campaign says the former Pennsylvania senator will still participate in two evening tele-town halls with Florida and Minnesota voters.

Santorum's current and former opponents have sent his family well wishes via Twitter. Mitt Romney tweeted, "Ann and I send prayers and best wishes for Bella's good health to Rick and Karen Santorum and their entire family."

Former presidential candidate Texas Gov. Rick Perry, who often said he prayed for Santorum and his daughter on a daily basis tweeted, "Lift up prayers for Bella and the Santorum family. tinyurl.com/89c98eg." Perry's wife, Anita, has a cousin with the same condition as Bella.

The former Pennsylvania senator often talks about his daughter on the campaign trail. In a November interview with ABC News, Santorum was on the campaign trail when Bella was at home with Santorum's wife Karen and was suffering from a cold. For a child with Trisomy 18, even something as simple as the common cold can be very dangerous because of the breathing problems they already suffer.

During an interview with Santorum and his daughter Elizabeth while driving from West Burlington to Mt. Pleasant, Iowa, Elizabeth called her mother to see how her sister was doing. It was clear it was a hard night and the candidate said being away from his family was not easy, especially in this situation.

"It's stressful because we are dealing with a little girl who a cold can kill her … we are always faced with a few days that are really touch and go, and you want to be there not just to physically help, but emotionally, because it is a very stressful thing," Santorum said. "It is certainly hard to keep focused on what you are doing here when things back home are not as good as you'd like them to be."

He said at the time it was worth it, though, because he's the right candidate to fix the country.

On the campaign trail, Santorum has said that Bella had multiple hospital visits her first year, including an incident so serious that Karen, a former neo-natal nurse, had to intervene and perform CPR on Bella and rush her to the hospital in time.

Santorum has said that was the last time Bella was in the hospital, a point of pride that usually brings down the house when he tells audiences on the trail.

One especially moving story Santorum told about his daughter at a presidential forum in November in Iowa, about that same hospital visit when Bella was 5 months old, he revealed he had not loved her as much because he was so afraid that she would not survive.

"I (had) decided that the best thing I could do was to treat her differently," Santorum said, becoming emotional. "To not love her, like I did, because it wouldn't hurt as much if I lost her.

"I remember holding that finger, looking at her and realizing what I had done. I had been exactly what I had said that I'd fought against at the partial birth abortion. I had seen her as less a person," he said. "It does hurt to say that."

The Santorums have seven children including Bella, but they lost a child named Gabriel in 1996 who died just hours after birth.

The Santorums also tell the story of when Bella was born, because of the gravity of her condition, they would have birthday parties daily, then weekly for Bella as she got better, to celebrate her life.

Karen Santorum doesn't often appear on the campaign trail because she is at home in Virginia caring for Bella.

In October, Santorum said at a debate that he was taking a red eye home from Las Vegas because his daughter had surgery that day. The campaign released a web video about Bella following that debate because they said they had so many inquiries from supporters about her health and they were moved by the "tremendous outpouring of support."

Bella was with the family in Iowa in the summer when Santorum was campaigning and more recently in South Carolina. Although due to her condition she does not appear with the family in crowds.

ABC News' Arlette Saenz and Emily Friedman contributed to this report.