BERLIN — As Friedrich Merz’s popularity plunges to new lows — compounding his already-weak coalition’s troubles little more than a year into office — the chancellor is traveling the country to persuade Germans that things remain on the right track. It’s not going well. Instead, Merz looks like he is only compounding his problems, often appearing out of touch and further alienating some of the very voters he can least afford to lose. A stop in Salzwedel, a town lined with half-timbered homes in