HER silver tongue honed by decades in corporate marketing, Carly Fiorina has used two debates, and a steely determination on the campaign trail, to climb near the top of the polls for the Republican nomination. But Americans should pause on her biggest professional credential for our highest office: a short, disastrous stint atop one of America’s iconic technology companies, Hewlett-Packard. The clearest measure of her performance — and the report card preferred by Wall Street — is H.P.’s stock price, which dropped by 52 percent during her tenure of almost six years. Yes, Mrs. Fiorina served during the worst fall...