LAST FALL, Erik Mercer, a Maine social worker and psychotherapist, saw one of his senators, the Republican Susan Collins, while he was waiting for a plane in Washington, D.C. Mercer, a Democrat, had approached Collins on a plane once before, after the 2016 election, to thank her for a ferociously worded op-ed she had published before the election calling Donald Trump “unworthy of being our president” and declaring that she would not be voting for him.
This time, he asked if he could sit next to her and then described the trouble he was having explaining to his children that the president was above the law, mentioning particularly the terrible things Trump says about women. Collins, he recalled, replied that she didn’t believe the president had said anything bad about…