Purists would strongly disagree, but the average conservative voter and the average libertarian voter are sometimes difficult to distinguish. Both believe in limited government and free markets. Both revere the Constitution. In fact, polls of Republican voters almost always lump conservatives and libertarians together, making it difficult to gauge the number of libertarians in the party.

Clearly, though, there is a sizable and growing portion of the Republican Party that identifies with libertarianism’s more free-market philosophy. Libertarianism, which Ronald Reagan called the “very heart and soul of conservatism,” is particularly popular among young people.

But there is also a significant number of Republican voters who long for a return of the culture wars. Rick Santorum represents that portion of the party. His nomination could aggravate the tension between the GOP’s libertarian and socially conservative wings.

Santorum’s paternalistic conservatism has free-market conservatives’ and libertarians’ hearts in a flutter. To many, Santorum represents a resurgence of Bush-era compassionate conservatism and a step backwards for the tea party, whose initial goal was to “end to this sort of moralistic big-government conservatism.”

Cato’s Gene Healy explains why Santorum’s voting record alarms libertarians:

By voting for the No Child Left Behind Act, he helped give President Obama the power to micromanage the nation’s schools from Washington; and by supporting a prescription drug entitlement for Medicare, he helped saddle the taxpayers with a $16 trillion unfunded liability.

Santorum voted for the 2005 “bridge to nowhere” highway bill, has backed an expanded national service program, and his compassionate conservatism has the Bono seal of approval: “On our issues, he has been a defender of the most vulnerable.” Rick Santorum: He’s from the government, and he’s here to help.

Santorum’s 2012 campaign platform even includes a pledge to “re-direct funds within HHS, so it can create public/private partnerships … for the purpose of strengthening marriages, families, and fatherhood.”

If you liked what the feds did to the housing market, wait till you see what they can do for your marriage.

It is not just Santorum’s voting record that frightens libertarians; it is his outward hostility to the libertarian movement. On one occasion Santorum stated, “I am not a libertarian, and I fight very strongly against libertarian influence within the Republican Party and the conservative movement.” On another occasion, speaking on the ascendancy of the tea party, Santorum declared, “I’ve got some real concerns about this movement within the Republican Party and the tea party movement to sort of refashion conservatism, and I will vocally and publicly oppose it.”

It is this vocal opposition that causes pundits to fear that Santorum’s libertarian problem will become a libertarian voter exodus during the general election.

As Philip Klein notes, “Nobody expects the Republican presidential nominee to be a libertarian purist, but it helps if he or she at least has a libertarian streak. In Rick Santorum’s case, he’s actively hostile toward libertarianism, and that’s an obstacle not only to him winning the nomination, but also to having a chance in a general election against President Obama.”

In an odd twist of libertarian fate, it is Santorum’s general election run that could most resemble Barry Goldwater’s landslide 1964 loss.

Thomas Grier is a third-year law student at The Ohio State University. A graduate of Arizona State University, Grier writes on constitutional law, politics and pro-growth policy.