MSNBC’s revamped primetime and weekend programming is already faltering, with dismal ratings, sharp audience drop-offs, and a primetime collapse from one of the network’s most promoted new faces. What was meant to signal a new chapter beyond Rachel Maddow’s dominance has instead exposed serious trouble. In a bid to reshape its identity amid changing leadership and a shifting cable news landscape, MSNBC launched several new shows: The Weekend, The Weekend: Primetime, and The Weeknight. But if the early ratings are any indication, viewers are not impressed. Take The Weekend, for example. Debuting at 7 a.m. on Saturday with hosts Jonathan...