Former Massachusetts governor Mitt Romney has pulled ads attacking Rick Santorum off the air in Pennsylvania while the former senator spends time with his ailing daughter.

Santorum cancelled his Monday campaign events to stay in the hospital with Bella, 3, who was hospitalized Friday morning.

“We have done this out of deference to Senator Santorum’s decision to suspend his campaign for personal family reasons,” Romney spokeswoman Andrea Saul confirmed.

Romney’s campaign asked for “Historic” to be pulled as soon as possible and kept off the air until further notice.

“While this was the earliest we could let them know due to station closures over the holiday weekend, stations will comply with this request as soon as they are technically able,” Saul added.

“Historic,” a negative ad highlighting Santorum’s 17-point loss in his 2006 reelection campaign, began airing in the Keystone State today.

The negative spot will be replaced on the air by “Conservative Record,” a positive ad highlighting Romney’s accomplishments.

Bella Santorum suffers from Trisomy 18, a rare genetic disorder that in 90 percent of cases kills children before they turn one. She is in the hospital for the second time since Santorum began running for president.

Santorum sees the April 24 Pennsylvania primary as a “must win” that will justify his continued campaign. Romney is investing heavily in the race, reserving $2.9 million in airtime time between now and primary day.

Campaign spokesman Hogan Gidley said on MSNBC Monday morning that Bella is doing much better and the candidate will return to the trail Tuesday.