Nashua, NH—During the Republican presidential primary debates it has been evident that no two candidates despise each other more than Rick Santorum and Ron Paul. Frequently when Paul spoke you could see Santorum shaking his head and rolling his eyes with an expression that seemed simultaneously aggravated and bemused.

It makes sense that they wouldn’t like each other. Their platforms are diametrically opposed.

Paul is a small-government conservative in the tradition of Barry Goldwater. He despises federal power and foreign policy adventurism.

Santorum is not so much a conservative as an interventionist. He would have the government intervene between a woman and her doctor. He advocates military interventions abroad. And while he wants to cut taxes for the rich and social spending for the poor, he has readily tossed aside his fiscal conservatism in favor of partisan or interest group politics.

Now the Paul campaign is going after Santorum. Paul’s hard-hitting commercials about Newt Gingrich’s apostasies helped play a role in Gingrich’s demise. It probably irks Paul to see Gingrich being replaced by Santorum, who is only marginally better from a limited government perspective. So Paul has released a blistering one-minute ad on television in South Carolina. The spot explicitly describes Santorum as another Gingrich, hitting Santorum for voting for earmarks, raising the debt ceiling and fundraising from lobbyists.

On the campaign trail Sen. Rand Paul (R-KY), Ron’s son who is speaking as his surrogate, goes after Santorum by implication. At the Hillsborough County Republican Committee Lincoln-Reagan dinner in Nashua, New Hampshire, on Friday, Santorum spoke shortly before Rand Paul. Santorum harkened back to 1980 when George H.W. Bush won the caucus in Iowa while Ronald Reagan won the New Hampshire primary.

“I’m told repeatedly by the press that New Hampshire is much more moderate [than Iowa], much more libertarian, much more concerned with fiscal issues,” said Santorum. “But they chose the broad contrast.” The implication is obvious: choose Santorum, the right-winger, to contrast more starkly with President Obama, rather than a more mainstream Republican such as Mitt Romney who currently leads the polls in New Hampshire. “Lead and be bold,” Santorum implored. (Although Santorum implied in those remarks that New Hampshire voters are more than just fiscal conservatives, the rest of his speech played to exactly that stereotype: he talked solely about fiscal issues, with no mention of social issues or foreign policy.)

Rand Paul echoed Santorum’s line about the desirability of the strongest possible contrast, but gave a very different definition of what that would mean. “That would be someone has never flip-flopped, never supported any part of Obamacare,” said Paul, in a clear dig at Romney and Gingrich, who in the past both advocated an individual mandate to buy health insurance and action to address climate change. But then Paul pivoted to a section that could only be aimed at Santorum. “The debt doubled our watch,” Paul noted, referring to the profligacy of George W. Bush and the Republicans in Congress. The only candidate who served in Congress during that era (other than Ron Paul) is Santorum. “Republicans passed Medicare Part D and No Child Left Behind, which doubled the size of the Department of Education,” Paul added. Santorum voted for both bills.

Then Paul proceeded to out-Reagan Santorum, remembering that his father was one of only four congressman to back Reagan in his 1976 primary bid to unseat President Gerald Ford. At the time Republicans such as Reagan wanted to abolish the Department of Education. Reagan abandoned that position when he was in the White House, but Ron Paul still supports it.

For as long as Santorum is in the race, the Paul campaign is likely to keep criticizing him. Ron Paul isn’t running to win the presidency, just as he isn’t in Congress to pass legislation. He seeks to reclaim the soul of American conservatism, and to him Santorum embodies its corruption.