IT’S NOT JUST RAND PAUL’S IDEOLOGY THAT DOESN’T MAKE SENSE…. When we think of Senate hopeful Rand Paul, we tend to think of his extreme, often-bizarre ideology. But it’s worth remembering that the Kentucky Republican has shared some of his policy ideas with the public, and they’re bizarre, too.

Republican Senatorial candidate Rand Paul wants to build a fence along the U.S.-Mexico border. It’s a rather ho-hum proposition in the larger context of conservative ideas — except that Paul wants that fence to be electric and he wants it built underground.

Among the variety of proposals to stem illegal immigration along the southern border, the construction of an underground electrical fence appears to stand alone on the extreme. There is little contemporary evidence of other Republican officials proposing such a project, even among the most conservative of the bunch. Indeed, when approached in the halls of Senate several weeks ago and asked about the idea (though not told who proposed it), National Republican Senate Committee Chair John Cornyn (R-Tex.) assumed it was a joke.

“I have not heard that,” the Texas Republican said. “Underground? What would happen? How would that work?”

For a change, I can relate to Cornyn’s confusion. Rand Paul’s website boasts of the Senate candidate’s plan to build “an underground electric fence,” but no one — not even Paul’s allies — has the foggiest idea what he’s talking about. When asked about the proposal, campaign aides won’t talk about it.

Does Paul mean some kind of electrified fence that would be shocking to the touch? If so, wouldn’t burying it underground defeat the purpose? Or maybe Paul means some kind of invisible, electrified fence — like those used with outdoor pets? If so, how does Paul propose getting human beings to wear the shock devices?

Maybe he means some kind of electric barrier that would zap people trying to cross? If so, wouldn’t people just step over it? Perhaps Paul would want it to be really wide, but given that it’s a 2,000-mile border, it would probably cost an enormous amount of money to construct this, if the technology even exists.

In what appears to be the only instance in which Paul elaborated on his idea, the Senate candidate said building the electric fence underground would help avoid the unfortunate symbolism of a Berlin Wall-like structure. That’s true, but it doesn’t explain how the contraption would work. Paul also said his plan would cost between $10 and 15 million dollars, which is fairly ridiculous on its face.

To the extent that policymakers will try to address immigration policy, the fact that Paul has a nutty idea probably doesn’t matter much — there are plenty of nutty ideas out there, and they’re easily ignored. But this is nevertheless a reminder that Rand Paul isn’t just an extremist on issues related to the role of government in society; he’s even on the fringes of libertarian thought. The seriousness with which he approaches policy issues makes it very difficult to find him credible as a candidate for the U.S. Senate.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.