David Boaz, executive vice president of the Cato Institute, writes in Politico that he finds Rick Santorum “frighteningly anti-libertarian.” I asked Boaz what he meant and to assess Santorum from Cato’s libertarian perspective. This is our Q & A:

What scares you about Rick Santorum?

Being philosophically minded, what scares me most about Rick Santorum is not his specific policy mistakes but his fundamental objection to the American idea of freedom. He criticizes the pursuit of happiness! He says, “This is the mantra of the left: I have a right to do what I want to do” and “We have a whole culture that is focused on immediate gratification and the pursuit of happiness . . . and it is harming America.” And then he says that what the Founders meant by happiness was “to do the morally right thing.” He really doesn’t like the idea of America as a free society, where adults make their own decisions and sometimes make choices that Santorum disapproves. In practice, I worry that he would continue and intensify Bush’s big-government conservatism, a federal government committed to reshaping individuals according to a religious-conservative blueprint.

In 2010 the GOP won on a small government, pro-free market message. Is it a mistake to pivot from that?

Every time Republicans have a big win — 1980, 1994, 2010 — it’s because Democrats have overreached on their big-government agenda and Republicans campaign on lower taxes and limited government. Every Republican strategist knows that smaller government is the unifying theme for Republicans and independents in this election. I think even Santorum knows it. I think he doesn’t really mean to get distracted into talking about homosexuality, contraception, and the outrage of separation of church and state. He just can’t help it. He starts talking; those topics come out. And that’s why he could deliver a landslide reelection to Barack Obama in the face of the biggest jump in the size of government since the Great Depression and the highest unemployment any president running for reelection has had to deal with since then.

Is Santorum a fiscal conservative?

Santorum is broadly speaking a fiscal conservative. He did try to reform entitlements, both welfare and Social Security. He got As and Bs from the National Taxpayers Union on spending issues, ranking anywhere from top 10 to middle of the Republican pack. But he supported No Child Left Behind, the Medicare prescription drug entitlement, the massive highway bill of 2005 and even the notorious Bridge to Nowhere. He bragged about his pork-barrel spending and trade protectionism for Pennsylvania. As president he’d probably resist tax increases, intend to spend less than Obama and come up with lots of schemes to subsidize marriage, children and local schools.