What better way to win Russian votes than to threaten the U.S. with nuclear attack? It wasn’t enough for Russia’s President Vladimir Putin to ban his only credible opponent from the country’s upcoming election. Nor was he apparently convinced that his ironclad control of Russian TV would deliver a sufficiently resounding victory. In last week’s annual address to Russia’s Federal Assembly, Mr. Putin threatened a new arms race, declaring that “efforts to contain Russia have failed” and showing video simulations of “unstoppable”...