EVERY talking head in the United States has spent the last week prattling on about Hillary Clinton’s emails.Fair enough. The former Secretary of State violated government rules in an apparent effort to keep her correspondence safe from scrutiny. That’s no small matter. But in the meantime, another politician has come from nowhere to dethrone Jeb Bush as the frontrunner for the Republican Party’s presidential nomination. His name’s Scott Walker.A few months ago, Walker was an obscure underdog with little more than an outside chance of becoming the nominee. Now he’s being seriously considered for the most important job on the...