The episode was not just another trade spat. It was also another attempt to rebrand Reagan’s record along Trumpian lines. Reagan remains an icon among many Republicans: He was elected by a large margin, won re-election by a landslide and left the presidency extremely popular with the American public. Mr. Trump, by contrast, narrowly won two elections and lost another, and his polling numbers are hovering in the low 40-percent range. Naturally, he’s sensitive about comparisons with his predecessor.