For a small-government conservative on the presidential campaign stump like Texas Gov. Rick Perry, a new federal regulation forcing farmers to get commercial drivers licenses would make a perfect example of Barack Obama’s Washington run amok.

Texas Gov. Rick Perry speaks to workers at a stop at D.C. Taylor Roofing in Cedar Rapids, Iowa,Tuesday. (AP Photo/Charles Dharapak)

But there is no such regulation.

During his debut in Iowa Sunday night in Waterloo, then again at on Monday at the Iowa State Fair Monday, Gov. Perry brought up the phantom “obscene, crazy” regulation in Texan terms.

“If you’re a tractor driver, if you drive your tractor across a public road, you’re gonna have to have a commercial driver’s license. Now how idiotic is that?” he thundered to the fair crowd in Des Moines, with the rejoinder, “What were they thinkin’?”

Here’s what they were thinking. Earlier this year, the State of Illinois began regulating certain kinds of farmers as commercial motor vehicle drivers, a move that caused a lot of consternation in the Illinois farming community, seeing as it would require stiff new driving tests, periodic drug testing and other hurdles. The Federal Motor Carrier Safety Administration stepped in to clarify whether the states had the right to do what Illinois had done, and on May 31, the U.S. Department of Transportation issued a public notice asking for comment on the commercial licensing of farm equipment…