RAND PAUL RETHINKS HIS OWN TAX POLICY…. In a handful of races this year, voters are hearing about a conservative idea that tends to exist on the fringes. The proposal has a nice sounding name — the “fair tax” — but it’s actually a plan to scrap the existing U.S. tax structure, and replace it with a national sales tax.

To crudely summarize, all federal personal and corporate income taxes, gift, estate, capital gains, alternative minimum, Social Security, Medicare and self-employment taxes would be swept away. In its place, we’d have a large national consumption tax. Since the wealthy spend a small proportion of their income, and everyone else spends far more, it’s an extremely regressive approach to tax policy.

In Kentucky, extremist Senate candidate Rand Paul (R) was asked about his endorsement of the idea. “I haven’t really been saying anything like that,” he told reporters.

That’s not quite true.

An anti-tax group on Tuesday released to The Associated Press a written statement from Paul saying he would support changing the federal tax code to get rid of the Internal Revenue Service, and he would vote to repeal the 16th Amendment. Paul’s statement called the federal tax code “a disaster” and said he supports making taxes “flatter and simpler.”

“I would vote for the FairTax to get rid of the Sixteenth Amendment, the IRS and a lot of the control the federal government exerts over us,” Paul wrote in a statement verified by his campaign.

Not surprisingly, Paul’s Democratic opponent, state Attorney General Jack Conway, thinks voters should be aware of this. “Working people are having a tough enough time making ends meet,” Conway campaign spokesperson Allison Haley said. “They can’t afford Rand’s plan to put a 23 percent sales tax on everything they buy — from groceries to gas to medicine.”

Pressed by reporters about his endorsement of the radical tax policy, Paul “declined to answer further questions on the topic.”

I wonder why.

The problem for Paul is that he seems to take positions on issues he doesn’t understand, and then can’t figure out a way to defend the ideas he endorses. It’s generally the first hint of a candidate who isn’t quite ready for prime time.

As for the campaign, polls show a very close contest. I wonder what would happen if Conway spent the next 19 days talking about “Rand Paul’s plan to put a 23 percent sales tax on everything Kentuckians buy — from groceries to gas to medicine.”

Steve Benen

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.