Sen. Rand Paul (R-KY) leaves the weekly Republican Senate policy luncheon at the U.S. Capitol February 3, 2015 in Washington, DC. (Chip Somodevilla/Getty Images)

It has become the Rand Paul pattern: A few weeks paddling vigorously in the mainstream, followed by a lapse into authenticity, followed by transparent damage control, followed by churlishness toward anyone in the media who notices. All the signs of a man trying to get comfortable in someone else’s skin.

The latest example is vaccination. “I have heard of many tragic cases,” said Dr. Paul, “of walking, talking normal children who wound up with profound mental disorders after vaccines.” Following the ensuing firestorm, the Republican senator from Kentucky insisted, “I did not say vaccines caused disorders, just that they were temporally related.”

In effect: I did not sleep with that causation.

Paul blamed his troubles on the “liberal media” — which, after a little digging, reported that, in 2009, he had called mandatory vaccinations a step toward “martial law.”

When Chris Christie commits a gaffe on vaccination and reverses himself, it indicates a man out of his depth. With Paul, it reveals the unexplored depths of a highly ideological and conspiratorial worldview.

The same dynamic was at work when Paul accused public health authorities of dishonesty about the true nature of the Ebola threat; or when he raised the prospect of Americans “typing an e-mail in a cafe” being summarily executed by a “Hellfire missile”; or when he accused Dick Cheney of supporting the Iraq war to benefit Halliburton; or when he accused the United States of provoking Japan into World War II; or when he criticized the application of the Civil Rights Act of 1964 to private enterprise. Wherever you scratch the paint, there is some underlying, consistent philosophy at work.

This, of course, is true of any thoughtful politician (which Paul certainly is). But while many prospective presidential candidates seek catchier ways to express their political philosophy, Paul must take pains to conceal the ambition of his ideals.

His domestic libertarianism provides no philosophical foundation for most of the federal government. As a practical matter, he can call for the end of Obamacare but not for the abolition of Medicare or Medicaid or the National Institutes of Health. Yet these concessions to reality are fundamentally arbitrary. The only principle guiding Paul’s selectivity is the avoidance of gaffes. Of which he is not always the best judge.

The same is true of Paul’s “constitutional foreign policy,” which he now calls (as evidence of his evolution) “conservative realism.” There is no previously existing form of “realism” that urges a dramatically weakened executive in the conduct of foreign and defense policy — which is Paul’s strong preference. He denies the legal basis for the war on terrorism, warns against an oppressive national security state and proposes to scale back American commitments in Europe, Asia and the Middle East. Paul is properly described as a libertarian noninterventionist.

His father, Ron Paul, is gleefully specific in his charge that American aggression creates the “blowback” of terrorism. The son qualifies the argument without repudiating it. “Some anger is blowback,” he now says. In 2009, he called his father’s theory a “message that can be presented and be something that Republicans can agree to.” A recommended reading list posted (briefly) last year on Paul’s Senate Web site included Chalmers Johnson’s “Blowback: The Costs and Consequences of American Empire” and Ron Paul’s “A Foreign Policy of Freedom.”

On both domestic and foreign policy, Rand Paul holds libertarian views that, if fully and publicly expressed, would bring new rounds of controversy. It is a difficult position for a candidate when every glimmer of authenticity is a potential blunder.

Paul is a talented politician, capable of embracing creative ideas (as on criminal justice reform). But it is increasingly difficult to identify his target political audience. Is it libertarians with a panting desire for establishment legitimacy? I had thought that part of the appeal of libertarianism was its defiance of elites.

By any objective measure, Paul is a strong presidential candidate. He is one of a few Republicans capable of raising the funds to run a national campaign. And he is one of the most consistently interesting candidates in the field. But he is likely to be interesting in self-destructive ways, as on the issue of vaccination. For all its flaws of length and cost, a presidential campaign strips away pose and pretense. And that is a particular problem for Rand Paul.

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