Washington — One measure of the effectiveness of a political movement is how it changes its opposition. And Donald Trump is in the process of driving portions of his Democratic opposition insane.

Hillary Clinton — whose warmth, integrity and down-to-earth style were the largest reasons for Trump’s election — has now publicly turned against civility. “You cannot be civil,” she explains, “with a political party that wants to destroy what you stand for, what you care about.”

The problem, of course, is that this describes politics in pretty much every time. What Clinton was struggling to address is a deeper question: How should liberals react to populism? And she is speaking for a certain temper within her ideological tradition — the one that proposes to fight fire with fire.

What does this look like in practice? So far, it means United States senators pulling childish stunts like committee walkouts. It means calling your opponents “evil.” It means protesters screaming to disrupt the Senate from the galleries. It means harassing opposition politicians at restaurants. It means charging and pounding the doors of the Supreme Court to chants of “Hey, hey, ho, ho! Kavanaugh has got to go!”

But is ethno-nationalist populism effectively fought with intemperate language, lame symbolism and pathetic nostalgia for the summer of ’68? Do Democrats really want to run Eugene McCarthy against Donald Trump?

The president is more than ready for that fight. “You don’t hand matches to an arsonist,” he recently said, “and you don’t give power to an angry, left-wing mob. And that’s what the Democrats have become. They would turn our country so fast into Venezuela.”

Every single word of this argument involves crass deception and absurd irony. Trump is the verbal arsonist par excellence. The purpose of his political rallies is to whip up a right-wing mob into frothing anger. He routinely calls for the jailing of political opponents. In criticizing the slowness of police efforts to silence protesters, he once complained: “Part of the problem … is nobody wants to hurt each other anymore.” Trump once incited violence against a protester with the words: “Knock the crap out of him, would you? I promise you, I will pay your legal fees.” Trump was preparing the ground to dispute the legitimacy of an election outcome in 2016 that did not favor him. In his swagger and threats, in his contempt for an independent media and disdain for democratic processes, Trump is the closest America has ever come to the vicious, oppressive populism of Hugo Chavez.

Yet Democratic tactics involving equal and opposite anger are allowing Trump to audition for the role of Richard Nixon in the 1968 presidential election. The president of chaos, dehumanization and violent threats intends to run as a symbol of social stability and order.

How can this possibly work? It may not. But Trump’s hand is strengthened when thinkers on the left attempt to argue that the anti-majoritarian elements of American democracy are undercutting the legitimacy of Republican government. Since Trump did not win the popular vote, the argument goes, and since the electoral rules are rigged in favor of Republicans to control the House and Senate, and since much of the Supreme Court has been chosen and approved by presidents and legislators without majority support, then Republican rule is an attack on democracy.

This may be fighting fire with fire, but it is also playing with fire. Never mind that everyone knows the rules of the Electoral College beforehand, and never mind that the disproportionate influence of some voters is part of the Senate’s constitutional design, and never mind that adverse redistricting has often resulted from the collapse of the Democratic Party in state governments. When both parties regard electoral losses as indications of electoral fraud and theft, our nation will enter a new stage of fragility. It will become easier to surrender to the irrational, to practice harassment and humiliation, and to turn to verbal and physical violence.

There are resources within political liberalism that would allow it to provide a compelling contrast to ethno-populism — a belief in universal human rights and dignity, an ideal of citizenship based on a shared creed, a vision of justice that includes the outsider and the struggling, a conception of politics that appeals to our better angels and common aspirations. Some rising Democrat needs to study up on President Franklin Roosevelt, and Sen. Robert F. Kennedy, and Gov. Bob Casey Sr. and Prime Minister Tony Blair. To eventually beat Donald Trump, liberals must re-master the language of unity and hope.

— Michael Gerson is a columnist for Washington Post Writers Group.