The effort to ban TikTok is back, and it could gain more strength after the midterm elections. Former Trump administration officials, a communications regulator, conservative commentators and several Republican lawmakers have been working in recent months to revive the Trump-era movement to ban TikTok, or at least to force a spinoff of the video app from its Chinese parent company. The suggestion that TikTok might disappear from app stores or stop working on U.S. phones might seem absurd to the millions of people who turn to it as a source of entertainment and information. But critics have never given up...