"But Santorum wasn't always so opposed to government-run schools--especially one Pennsylvania cyber charter school that offered students free computers, internet service, and online classes. Between 2001 and 2004, that online school allowed the Santorum family to live in Virginia, while sticking Pennsylvania taxpayers with a $100,000 bill."

Many GOP voters also want a nominee they believe can defeat President Barack Obama, a factor that is perceived to be Mr. Romney's area of strength. In 2006, Mr. Santorum's fiery brand of social conservatism turned off voters in Pennsylvania, and in particular in the Philadelphia suburbs, the sort of swing areas key to any candidate's 2012 efforts.  "Anytime someone is rejected by home-state voters, it will give other voters pause," said Jim Roddey, chairman of the GOP in Allegheny County, Pa., who called 2006 "a real liability." Voters "will say, 'What do they know about him that we don't?' " he added. Mr. Roddey has worked with Mr. Santorum and considers him a friend, but is backing Mr. Romney.

"But there's at least one blemish on Santorum's conservative record: his vote for the Medicare prescription drug entitlement in 2003 -- the biggest expansion of the program since it was created in 1965 and a bill that the Congressional Budget Office said would add nearly $400 billion to cumulative budget deficits over the first ten years after its enactment.  Fiscal conservatives such as Paul, DeMint and Santorum's fellow Pennsylvanian Pat Toomey voted against the Medicare prescription drug bill, as did Sen. John McCain of Arizona."