Democratic presidential hopeful Barack Obama learned an important lesson from the 2004 presidential campaign: Don’t be passive about false rumors. When Democratic nominee and Vietnam War veteran John Kerry, who served with distinction in the U.S. Navy and won multiple Purple Hearts for wounds in battle, was attacked for a lack of patriotism, his campaign was slow to respond. Obama won’t be so passive. The scurrilous attack on Kerry, largely funded by Houston homebuilder Bob Perry, a Republican Party sugar daddy, was outlandish. A group called Swift Boat Veterans for Truth posted the ads, coining a new term for dirty...