People on the left believe that Mr. Trump has incited hatred against minorities, and boasted about grabbing women by their genitals. Democrats think that the president and his family are blatantly profiting off the presidency and that he welcomed the help of a hostile foreign power during the election. All this is grounded in fact.

Facts aside, there is an emotional symmetry between the conservative reaction to past Democratic presidents and the liberal response to Mr. Trump. Suddenly, left-of-center people get what it’s like to have a president who is the living negation of all they value, a president who makes them ashamed before their children and terrified for their future. Now they’ve learned what it’s like to worry that malevolent foreign conspirators are manipulating American affairs. And these feelings, it turns out, are an extremely powerful goad to political action.

I saw this recently in Georgia’s Sixth District, a conservative area that had sent to Congress first Newt Gingrich and then Tom Price, now Mr. Trump’s secretary of health and human services. I was there to report on the special congressional election to fill Mr. Price’s seat. Ahead of the April 18 open primary, a Democrat, Jon Ossoff, was showing unexpected strength. In the event, he only narrowly failed to win the district outright, and goes forward to a June runoff against the leading Republican vote-getter.

Lots of outsiders were paying attention to the race; Mr. Ossoff raised a staggering $8 million for what was widely seen as a referendum on Mr. Trump’s presidency. On the ground, though, the people powering the campaign were locals, many of them previously apolitical suburban women shocked into action by the presidential election.

In November’s aftermath, Amy Nosek, a 42-year-old stay-at-home mother of two living in an affluent Atlanta suburb, sank into depression, though she’d never been depressed before. “I didn’t even want to go pick up my kids from the school bus because I didn’t want to talk to the other parents, or see anybody,” she told me.