Saturday was mild and cloudy in Philadelphia—good marching weather for the thousands of anti-Trump protesters who gathered at City Hall and made their way down Market Street to Independence Hall and the Liberty Bell. The atmosphere was upbeat—festive, almost. Many members of the crowd were carrying homemade signs, and their chants filled the spring air: “What do we want? Trump’s tax returns. When do we want it? Now.” “We want a leader, not a tax cheater. We want a leader, not a friggin’ tweeter.”

Eighty-five days into the Trump Presidency, similar scenes played out across the country: from Los Angeles to Boston, from Seattle to Raleigh. In Palm Beach, about three thousand people** **kicked up a racket near Trump’s Mar-a-Lago resort, where the President was spending yet another weekend.

The First Golfer wasn’t pleased. To avoid the protesters, one of whom was carrying a sign that said, “Twinkle Twinkle Little Czar, Putin Put You Where You Are,” his motorcade was forced to take a circuitous route back from Trump International Golf Club, where he had played his sixteenth round since taking office. (That figure comes courtesy of a tally by the Palm Beach Post.) The following morning, Easter Sunday, Trump took to Twitter, grumbling, “Someone should look into who paid for the small organized rallies yesterday. The election is over!”

The protests weren’t small, of course, and nobody paid for them. They were the latest manifestation of a popular movement that Trump himself has inspired, one that has established itself as an important presence on the national political scene, and with which Trump and his Republican allies and enablers increasingly have to contend.

During their two-week Easter break, many G.O.P. members of Congress were confronted by constituents upset over the Republican effort to dismantle Obamacare. Politico, which dispatched reporters to nearly a dozen town-hall meetings, reported, for example, that the Colorado representative Mike Coffman, a relative moderate, was confronted by a lifelong Republican who demanded that he commit to limiting premiums for people with preëxisting conditions. In Graniteville, South Carolina, a crowd chanted “You lie!” at Joe Wilson, the Republican congressman who famously shouted out the same phrase during a 2009 address to Congress by former President Obama.

Of course, most of the people who are marching and protesting at Republican events might not be G.O.P. voters. But they aren’t all Democratic activists, either. Indeed, what is striking is how many people Trump has mobilized who previously didn’t pay very much attention to what happens in Washington. He has politicized many formerly apolitical people; ultimately, this may be among his biggest achievements as President.

At anti-Trump rallies, the organizers tend to be activists, but the protesters are of all sorts: college graduates outraged by Trump’s nativism; office workers angry that he won’t release his tax returns; doctors and nurses worried about the health-care system; retirees worried about their grandkids; and Americans from all walks of life who think that Trump isn’t fit for office and represents a grave danger to the country.

The troubles that Trump has encountered in office, far from diminishing the protest movement, have only encouraged it—and for good reason. If the past three months have demonstrated anything, it is that, even in a political system tainted by money and influence-peddling, political participation does matter. Federal officials, judges, Democratic and Republican congressmen, even Trump himself—they all pay attention to public activism and public opinion.

Take the Administration’s two attempts to enact an anti-Muslim travel ban. Would the federal courts have blocked the measures without the mass protests that the first ban engendered? Or recall the Ryan-Trump health-care bill. While the defections of the ultra-conservative Freedom Caucus played a big role in the bill’s failure, so did the protests at G.O.P. town-hall meetings and the campaign to highlight how the measure would undercut affordable coverage for the old and sick.

These were two successes for the anti-Trump forces, as was the downgrading of Steve Bannon, the White House’s chief political strategist. To the extent that the goal of the resistance is to make sure the checks and balances in the American political system work as intended, and to prevent the emergence of an overweening Presidency, or a potential despot, it seems to be succeeding. Although Trump would never admit that he is backtracking, he has been forced to make some concessions to reality. But there is no room for complacency. Far from it.

Despite the tax-day protests, the President has no intention of releasing his returns, much less of setting up a proper blind trust for his business assets, or of separating his family from the conduct of government. Inside the White House, he appears to be relying more and more on his daughter Ivanka and son-in-law, Jared Kushner. Elsewhere in government, as the Times reported over the weekend, he is busy installing former lobbyists to oversee their former clients.

In many policy areas, the Trump Administration remains determined to roll back the clock in ways that will be difficult to stop. Protest marches won’t prevent the E.P.A. from whittling away at environmental regulations, the Justice Department from failing to enforce civil-rights laws, or the National Labor Relations Board from ruling in favor of big businesses.

Then there is Trump himself. Throughout his career, he has shown a willingness to do virtually anything, and to take huge risks, to protect his position. There is no reason to expect anything different now. In the past couple of weeks, he has pivoted to national security, ordered the bombing of Syria, presided over the detonation in Afghanistan of one of the biggest conventional weapons in the U.S. arsenal, and made threatening noises toward North Korea.

In foreign policy, unfortunately, Presidents are given wide latitude. Particularly during crises, Congress tends to defer to the Commander-in-Chief, and the judiciary can’t pull him back from the brink. But there is still the right to protest. And this seems like a good time for some peace rallies.