President Obama\'s campaign Tuesday said Mitt Romney would add $2 trillion to the deficits in 10 years and Rick Santorum would add nearly twice that. The Hill newspaper said the attacks were part of the Obama campaign\'s new strategy against his Republican challengers -- Santorum, a former U.S. senator from Pennsylvania, and Romney, a former Massachusetts governor. Despite their claims to be budget hawks, the Obama camp says the Republican contenders propose tax cuts and new defense spending that would add trillions to the national deficit over 10 years. The Democratic president\'s campaign said Santorum would have to shut down the government or chop retiree deficits to match Obama\'s deficit reduction. Obama campaign economist Jeffrey Liebman ripped into the Republican candidate in a conference call with reporters. \"To match the president on deficit reduction, Santorum would have to eliminate all defense and non-defense discretionary spending,\" The Hill quoted Liebman as saying. Discretionary spending outside defense includes government \"overhead\": salaries, office space and other necessities, without which the government would shut down. \"Santorum is definitely operating in fantasyland,\" Liebman said. \"By far, these are the most unrealistic budget plans I have ever seen.\" The White House has been playing defense over its proposed 2013 budget, which the Republican say use gimmicks and huge tax increases to claim $4 trillion in deficit cuts over 10 years, The Hill said.