Return the power to the people.

Donald Trump rode to the presidency on the strength of that core call to revolution, telling his supporters in his inaugural address on Friday that his election was the result of people taking control of their government.

Trump might not have fully understood what he was unleashing. Sometimes the revolution you preach is not the only one you get.

When all is said and done, Saturday’s Women’s March demonstrations in hundreds of cities across the nation are likely to be the largest simultaneous protest in the United States, and they were part of almost 700 “sister” marches around the world that drew millions. The variety of causes they espoused was endless, but at the root of each was a message Trump and his supporters understand well.

I am here. I matter. Hear me.

Trump was not wrong when he crafted his victorious campaign on bashing establishment elites and lacerating powerful politicians as disconnected from the people they represent. Many of the people who voted for him felt they had been left behind. Now, he’s being reminded that many others, also frustrated by the failed promises of the political class have zeroed in on an opponent that is the catalyst for their discontent with a pointed chant: “Welcome to your first day, we will not go away.”

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The multi-generational outpouring, that included men, was stunning. The crowd in Washington, the initial focus destination of the Women’s March, was estimated at half a million. Chicago’s rally drew some 150,000. Midtown Manhattan was brought to a standstill by a crowd police put at 400,000. Los Angeles might have had even more.

Overseas, more than 100,000 came out in London and many thousands hit the streets in places like Paris, Berlin and Amsterdam, and nearly two dozen of the 88 people on the Isle of Eigg, off the coast of Scotland, tweeted a picture of their protest. “Today we marched to say a world where equality and justice lead the way, tolerance, kindness and communities thrive,” they wrote. Many overseas are alarmed by the rising international tides of nationalism and anti-globilization, also sounded here by Trump.

The president motivated many American marchers who were insulted by his vitriol and his misogynistic behavior and language during a brutal campaign, and who were heartbroken by Hillary Clinton’s loss. Most of the causes promoted Saturday — from gender and abortion rights to civil rights to Planned Parenthood to immigration — are things they say are threatened by Trump’s administration.

Their energy and enthusiasm were reminiscent of the iconic Vietnam War and civil rights protests of the 1960s. But Saturday’s marches were distinctive in how much more quickly they came together. Part of that is due to our relentless 24/7 news cycle. Spreading the word is much easier in the age of social media. And it seems likely that these kinds of demonstrations will continue to pop up unexpectedly. They are the beginning of an oppositional force to Trump and what he represents.

This passion play seems destined for a long run because of the breadth of the emotion, the range of people feeling it and the way their frustrations are turning into fears. Feminist icon Gloria Steinem called it “the upside of the downside.”

But no celebrity or politician will control this new activism. It is organic and unpredictable. These marches were not inspired by any political party, certainly not the demoralized and fractured Democrats, and not the Republicans who have tied themselves to Trump.

This new activism should not be dismissed. Its demands are many and its leadership unknown. There is a new, wide-open system of democracy unfolding with little understanding of where it will lead. It may inspire and bring new waves of people to seek elective office. Or to vote. But will it change our system in ways we can’t yet imagine?

Trump has regularly criticized protests, and his critics, in the past. In a discordant appearance at CIA headquarters Saturday, he again tried to discredit the news media and said they lied about the size of his small inaugural crowd. He said it was at least 1.5 million, a figure quickly dismissed by all independent analyses.

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Later, White House spokesman Sean Spicer read an extraordinary statement that seemed to be written in an alternative reality. He didn’t use a specific number, but insisted that Trump’s crowd was the largest to witness an inauguration “around the world.” The statement warned the media not to make any estimates of the size of the Women’s March — because Trump needs to believe that the sea of humanity he saw on his way to CIA headquarters was not bigger than his.

Trump must understand that displays of democracy are healthy for the country he now leads. The movement he provoked is sprouting wings. Returning the power to the people means returning it to all the people.

The roars that broke out over and over on the National Mall Saturday could be heard at the U.S. Capitol and the White House.

Trump should listen.