White nationalists carry torches on the grounds of the University of Virginia, on the eve of a planned Unite The Right rally in Charlottesville, Virginia, August 11, 2017. (Evelyn Hockstein/For The Washington Post)

Charlottesville. Berkeley. Houston. Three dots that lead to something urgent about our politics.

Let's connect them.

Wanna-be Nazis parading by torchlight through Charlottesville was a radical moment. Masked leftists marauding through Berkeley was another radical moment. Radical politics are the most dangerous kind, whether they arise from the right or the left. Around the world, the past 100 years have been an orgy of wars, genocides, famines and purges — the bloody fruits of various radical ideologies. Americans ought to be on guard.

Houston, battered, sodden, unbowed, stands for the opposite. Radicals emphasize and inflame political differences, which they find everywhere because for radicals everything's political: what you wear, what you eat, what you enjoy. The Khmer Rouge in Cambodia murdered people for wearing eyeglasses. The Islamic State radicals of Raqqa lopped off the head of a teenager caught listening to Western music.

In Houston, politics ended at the water's edge. Within hours of the first raindrops, the highways of Trump Country filled with pickup trucks towing boats. This flat-bottomed flotilla rescued people by the thousands, black, brown and white, regardless of voting history, religious preference or passport status.

This affirmation of shared human dignity is the serum that largely inoculated Americans against the deadly lure of radicalism. But while this spirit is strong in times of disaster, it is sagging on the political front. Liberals and conservatives must come together to revive it.

Say what? Liberals and conservatives together?

You see, Charlottesville and Berkeley are rampaging reminders that the political spectrum is much broader than we Americans are used to acknowledging. The spectrum runs far beyond Republicans and Democrats, from fascism to communism and from tyranny to anarchy. Conservatives and liberals are actually shoulder to shoulder at the center of this range.

We can wage intense debates across the liberal-conservative divide precisely because we share common assumptions and principles. Ronald Reagan and Walter Mondale, one a true conservative, the other a true liberal, vied for the presidency in 1984 while sharing the conviction that individuals are created equal and endowed with certain inalienable rights, including life, liberty and the pursuit of happiness. That speech and conscience are free. That government is fettered by the rule of law and accountable to the people.

They argued over the best means to achieve these shared ideals. And because those were less radical times, it was easy to accentuate their differences while taking the ideals for granted.

Thomas Jefferson put this heritage succinctly in the wake of the bitterly polarized election of 1800 . Party does not come first. As Americans, he declared in the terms of his times, "we are all Republicans, we are all Federalists."

Today's parties are accustomed to placating their radical elements with gestures and dog-whistles. But converging forces — including niche media, social networks and partisan gerrymandering — have tipped power from the center to the extremes, where radicals will no longer be placated.

These forces gave us perhaps the most radical presidential election in American history last year. The ostensibly conservative Republican Party was taken over by a man who stands against core conservative values such as prudence, order, tradition and free markets. Meanwhile, the ostensibly liberal Democratic Party was nearly hijacked by a socialist.

The fascists who invaded Charlottesville and the anarchists rioting in Berkeley may appropriate some language of liberty and rights. But in their radicalism there's no room for the spirit of Houston. There is only division.

Principled liberals and conservatives need to wake up to this peril. The solid center that has defined American politics for generations is under assault by empowered radicals on both sides. The old game of stirring big battles over small differences only serves to drive more people to the extremes. While the parties continue to demonize each other in hopes of winning the next election, they are feeding beasts that could devour them both.

The center still holds in many of our local and state governments. Some centrists remain in both parties of Congress, while others inside the White House maneuver to tame the Oval Office radical. But on the whole, we see only politics as usual from party leaders, the same old wedge issues, empty slogans and personal attacks. As if the storm is sure to pass.

We need leaders who can read the clouds of Charlottesville and Berkeley for the genuine menace they pose. Who, in the spirit of Houston, can shelve their differences, climb into their boats, and begin collecting all the stranded Americans they can find. Our pragmatic, can-do, solution-seeking people, regardless of party, are marooned in the radical flood.

There's no time to waste. The water is rising.

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