Move over, Bill Ayers. This week, Republican activists have a new Public Enemy #1. It’s ACORN, the once-obscure community-organizing group that boasts of having registered 1.3 million new voters. Republican officials and advisers to Sen. John McCain have accused ACORN (the Association of Community Organizations for Reform Now) of rampant voter-registration fraud. Indeed, officials in states including Pennsylvania, Ohio, Florida, Nevada, North Carolina, Indiana and Connecticut now are looking into accusations that ACORN workers turned in thousands of fraudulent or duplicate voter-registration applications. (The Dallas Cowboys magically filled out voter registration forms in Nevada, for example.) So what exactly is...