Mr. Kobach is pushing the myth that voter cheating is rampant. But he has utterly failed to document that, despite his Javert-like zealotry as secretary of state. In fact, the federal ruling against him said there was evidence of only three instances across 18 years in which noncitizens voted in Kansas.Mr. Kobach has not stopped at his state’s borders. He has been a principal contributor to the Republican Party platform. He wrote two pages of hard-edged immigration policy centered on Mr. Trump’s hateful fantasy of a wall that the plank trumpets “must cover the entirety of the southern border.” He helped write a plank condemning the Supreme Court’s 2015 ruling that legalized same-sex marriage nationwide. He also helped write another setting the Republican Party squarely against any ban on assault rifles and large-capacity ammunition magazines.