Mitt Romney pulls negative ads in Pennsylvania 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. "Historic," a negative ad highlighting Santorum's 17-point loss in his 2006 reelection campaign, began airing in the Keystone State today. The ad, via Politico: Romney's campaign asked for "Historic" to be pulled as soon as possible and kept off the air until further notice. Stations could not be contacted over the weekend, due to the holidays. 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 told Fox News Channel on Sunday that "we have a full slate of events on Tuesday and, hopefully, he'll be able to be back out on the trail."