If President Donald Trump’s first two weeks in the White House have been defined by anything, it’s protest. Just a day after Trump’s inauguration, millions of people around the country demonstrated as part of the Women’s Marches — potentially the biggest single day of protests in American history. And over this past weekend, thousands of people flooded airports to protest Trump’s executive order banning refugees for 120 days and travelers from seven Muslim-majority countries for 90 days.

Many Americans are, it’s safe to say, ready to protest Trump’s presidency.

But can these protests be successful? Will they be the start of a bigger movement? And what makes a protest successful, anyway? What makes it evolve from one march to a broader movement with serious political sway — the kind that can get policy change done?

I turned to experts on social movements to answer these questions.

They cautioned that it’s too early to judge just how the Women’s March and other protests will shake out. This is key: Change takes time and effort. So it will be a few months or years before we have a better idea about what these protests will accomplish.

So what should we watch out for? Experts all echoed one thing: One march or single day of protests is not enough. Demonstrations have to be enduring and build up to a broader movement to get things done — one that reaches out to the public, media, and politicians in numerous ways, from letter-writing campaigns to lobbying to supporting friendly candidates for political office. That’s what, experts said, made movements as disparate as both the civil rights movement and the Tea Party successful.

That’s not to undermine the value of a protest on its own. A big day of demonstrations can be key to getting a broader movement off the ground or catalyzing a cause. But if protesters want to inspire enduring change, they’re going to have to aim much higher. Only then will they successfully get the policy and political change that they seek.

A protest can be very valuable on its own

The experts I spoke to went to great pains to clarify that it’s not that they see a march or protest as useless. To the contrary.

“Getting people in the street and having them commit to a full day like that shows commitment,” Dana R. Fisher, a University of Maryland professor who studies protest movements, told me. “It shows people’s willingness to show more action than what might be involved in doing what we call ‘armchair activism.’”

A protest can be good for protest organizers, who can see that participants really are committed (or not) to their cause if people show up for action. High attendance sends a broader signal to the public, media, and politicians that this is something a large part of the country is taking seriously enough to at least temporarily disrupt their lives and speak out.

We saw some of this with the recent Women’s March. When the media and politicians saw that more than 4 million were gathering to speak out for a feminist cause and protest Trump’s lewd remarks about women, it drew widespread attention across all major news outlets. Prominent politicians, like Massachusetts Sen. Elizabeth Warren, got on board. Even Trump jumped into the fray, tweeting, “Watched protests yesterday but was under the impression that we just had an election! Why didn't these people vote?”

Similarly, past protests have helped draw attention to new causes. The first time most Americans heard of the Black Lives Matter movement was when activists took to the streets of New York City and Ferguson, Missouri, to demonstrate against killings of black men by police officers. And the Tea Party became a mainstream political group as it disrupted politicians’ town hall meetings and marched on Washington, DC.

Or consider the civil rights movement. It was a sprawling movement that involved a range of tactics — from protests to directly lobbying the president. But the image of the civil rights movement that pops up in many Americans’ heads is the 1963 March on Washington and the iconic “I Have a Dream” speech by Martin Luther King Jr.

But what makes an individual protest successful? According to Fisher, critical mass is key. It can depend on where the protest is or what its purpose is, but she estimated that 100,000 people is the tipping point for a major city like Washington, DC. Those kinds of numbers will draw widespread media and public attention.

Other factors can also play a role. More disruptive demonstrations can draw more attention even if they’re carried out by smaller crowds. The classic example is of protesters who chain-link themselves to a building or some other object: By disrupting someone’s — particularly a corporation's or politician’s — plans, such demonstrations force others to pay attention even if they don’t want to.

A recent example of this is the Occupy Wall Street movement, in which hundreds or thousands of demonstrators literally “occupied” public spaces to make their presence well known to the public, media, and authorities and protest income and wealth inequality in America. This sometimes forced confrontation between police and the protesters, such as when police cleared Zuccotti Park in New York City of the demonstrators — the kind of confrontation that will naturally draw media attention.

Once that kind of media attention is drawn in, the public is confronted with questions about the protests: Why are these protesters here? What do they hope to accomplish? In that way, just one day of big protests or marches can force a lot of people to talk about the issues that a group of protesters is demonstrating about.

A single march or protest “shapes media coverage of issues,” Ziad Munson, a Lehigh University professor who studies social movements, told me. “It helps define what issues are considered important and what will be focused on.” He added that protests can also push “those who are in positions of power, who are sympathetic allies, to take a stronger stand against those same things that the marches is taking a stand against.” The Women’s March, he said, already achieved these two objectives.

One point of caution: There are limits to how disruptive protests can be, and violence in particular can seriously backfire.

A riot may draw more attention to the desperation a certain group feels. The 1960s civil rights riots, for instance, drew enough attention to police abuses that they led to the creation of a federal commission that pushed for policing reforms. But riots can also justify a harsh government or public crackdown that mitigates or eliminates any gains from the protests. So the same 1960s riots helped build support for the “tough on crime” policies of the 1970s, ’80s, and ’90s, which in effect made police even more aggressive than they had been in the past.

University of Denver professor Erica Chenoweth, in her research on violent and nonviolent demonstrations worldwide, has found that violent protests can mobilize a push for reform when compared with doing nothing. But nonviolent actions succeed at much higher rates than violent campaigns.

“It’s often the case that doing something elevates the cause more than doing nothing,” Chenoweth said. “That doesn’t mean that violence was necessary.”

Real movements do more than lead rallies and protests

With all of that said, a protest is typically only one part of a successful movement. “If you look at movements that have been successful in the past, there is this full range of tactics and issues,” Fisher said. “When they’re successful, they use more than marching in the street.”

The experts I spoke to listed all sorts of other tactics that make up a successful movement. There’s calling, petitioning, and writing to politicians, or lobbying them. There’s boycotts. There’s getting businesses on board with your cause. There’s building more formal groups at the local, state, and national level. There’s running candidates for office or supporting candidates that meet certain criteria. And certain resources, such as cash and legal aid, are necessary to help set up big events and guarantee that your followers will get help in case a protest or march goes wrong.

Time and time again, experts named the Tea Party as a successful example of all these facets of protest movements. The Tea Party, which spoke out against what activists saw as the excesses of President Barack Obama’s government, came into the national spotlight through protests. But then it grew: Tea Party members directly called their legislators to support and oppose certain legislation. They drew support from business interests, like the Koch brothers. They put forward candidates in primary elections — forcing Republican politicians to either move to the right to match Tea Party positions or seriously risk losing an election.

And now the Tea Party is an enormous faction of the Republican Party — one that can literally reshape the party’s leadership. (Just ask former House Speaker John Boehner, who was ousted in part due to widespread Tea Party opposition.)

That doesn’t mean that all of these steps are necessary for every movement. Exactly what a movement needs to do depends on what kind of victory it’s seeking.

Scholars listed several kinds of victories that a movement can accomplish. They may just want to get a lot of people out on the streets to draw attention to an issue. They can empower a certain group of people. They can change a cultural narrative. Or they can — in the trickiest form of change — directly influence policy and political change.

Knowing what you want to achieve is key to how you set up your movement. For example, Occupy purposely never integrated into the political establishment in the same way the Tea Party did. That limited Occupy’s ability, at least in the short term, to get policy changes. But through its big demonstrations, Occupy still managed to succeed in a crucial way: It changed the cultural narrative by bringing phrases like “the 1 percent” and “the 99 percent” to mainstream political discussion — the kinds of phrases that, for example, Vermont Sen. Bernie Sanders often used in his unexpectedly strong campaign against Hillary Clinton in the 2016 Democratic primary election.

“One of their goals was not really to attain policy change,” Michael Heaney, a University of Michigan professor and co-author of Party in the Street: The Antiwar Movement and the Democratic Party after 9/11, told me. But “they changed the conversation. They helped to set the agenda.” And that could, in the long term, lead to bigger political and policy changes.

Experts said activists should also understand whether it’s even possible to make the changes they want, or what potential cultural or political barriers their desired policy change faces. Does the policy being changed directly benefit people? What powerful interest groups could successfully counter their efforts? Do protesters have important allies in Congress and state legislatures? These are some of the questions would-be protesters have to ask to gauge if a movement stands much of a chance in the first place.

“How much progress can be made depends on how responsive policies are to pressure,” Heaney said. “Some are. Some aren’t.”

Movements have to keep people engaged

Establishing ways to meet and communicate among members is also key to continuing the momentum of movements. For example, the civil rights movement leveraged black churches as a point of organization, while LGBTQ advocates have drawn on places like gay bars and supports for large marches before. These places and events help foster crucial personal relationships.

“People often need personal connections with the movement,” Fabio Rojas, an Indiana University professor and the other co-author of Party in the Street, told me. “When an individual has a personal relationship with another person in the movement — could be a friend, a spouse, a co-worker — they’re more likely than other people in the movement who don’t have these connections to keep participating and escalate their participation.”

Munson of Lehigh University said he often saw how crucial this is while conducting his own research into social movements.

First-time protesters, he observed, are very often “not there because they’re strongly motivated by issues or passions about a particular thing. They’re often there for, really, kind of ordinary reasons: because their sister was going, because they saw a lot about it on their Facebook feed and they went with some neighbors, because they went to support their mom, because they were just simply interested.”

He added, “So the real question is how many of those people who have had their first taste of activism can be captured by organizations that can then put their activism to work in a more sustained way.”

Knowing this, social movements can build special events that bring people together.

Take, for example, campaigns in which people get together to stuff envelopes with mailers that they then send out to potential supporters. “The positive impact of a campaign like that,” Munson said, “is at least as much about as the individual activists who got together to stuff those envelopes as it is the recipients who got those envelopes once they’re sent out. Because it brings people together and sustains their activism, it lets them tell their stories, it lets them understand the issues better, it makes them more committed. So then they’re much more likely to say yes when the next, bigger ask is made.”

But even if protest groups do all of this right, they should also plan for an eventual drop in public interest.

“Remember that waves of a movement are a finite thing: Just as it goes up, we know that it will eventually go down as well,” Heaney of the University of Michigan said.

For example, right now there is a lot of interest in Trump’s presidency. He has, after all, been in the Oval Office for less than a couple of weeks, and in that short time he’s already enforced controversial policies through his executive orders. But over time, the excitement may simply die down.

Organizers in the Women’s March and various anti-Trump protests should plan for this. When a controversy is in full blast, movements should take as much advantage of the situation as they can to get their message out. But when the news cycle calms down, they should also find other ways to keep followers engaged to achieve the policy and political goals they want.

That’s what the Tea Party did: It leveraged the controversy around Obamacare when the legislation was getting through Congress, and then it set up vast communication networks that kept allies — both in the public and in Congress — in touch. All of that helped build the Republican-dominated government of today.

There are some other traps that protests fall into again and again

There are also traps, experts said, that the burgeoning anti-Trump protest movement should watch for and avoid.

One such trap: focusing too much on protests and marches.

Some experts cited Occupy as an example of falling into this trap. While it’s true that Occupy helped change the narrative by putting income inequality at the forefront of American political discussion, its solely protest-driven approach also made it much harder to directly reach politicians and potential allies in government. As a result, it has yet to achieve concrete policy changes, especially at the national level.

In contrast, the Tea Party, which was quick to build a political infrastructure around its protests, is arguably seeing the fruits of its labor flourish right now.

“The level of success they [Occupy] have had in terms of concrete change pales in comparison to what’s probably going to happen with the Republican administration right now,” Rojas said. “It’s not just the fact that Donald Trump won the election. … It’s that he’s now backed by a Republican legislature, and the Republican legislature came from two or three cycles of Tea Party members running in every primary possible.”

Another risk is having unclear goals. It’s one thing to show up in the streets in huge numbers, but if no one has any idea why all these people are in the streets, interest will eventually fizzle out.

To this end, one of the most common mistakes that researchers cited is when protests dilute their message simply to bring in more people. This could lead to a bigger march, but it could also make that march unfocused.

Let’s say all 162 million American women and girls were on board with the Women’s March. That would be good for organizers, but women, just like any demographic group, have varying political opinions and goals.

For example, 57 percent of women, according to a 2016 Pew Research Center survey, say that abortion should be legal in all or most cases, while 40 percent say it should be illegal in all or most cases. This could cause tensions down the line if the Women’s Movement seeks, as it already has, to push for abortion rights.

It may sound obvious, Rojas said, but it’s true: “The bigger your group, the harder it is to organize.”

But movements can still build bridges among those who sometimes or often disagree. In the case of the Women’s March, Heaney said, “It’s not hard to imagine that there are women who are pro-life but yet don’t want to be sexually assaulted.”

He named his wife as someone who’s appalled by Trump’s sexist behavior and opposes abortion rights. There are “women who are pro-life but think that immigrants have a place in this country [and] women who are pro-life but would like to be paid what they deserve.”

Another common trap: becoming too partisan. Take the antiwar movement of the 2000s, when George W. Bush was in the White House. The movement pushed against the wars in Iraq and Afghanistan and the expansion of government powers — such as wiretapping, surveillance, and torture — that Bush deployed while in office. Democrats, naturally, latched themselves onto the movement, seeing it as a persuasive way to hit the Republican president, especially as the Iraq and Afghanistan wars drew on for years and years. Pretty soon, the antiwar movement and Democratic Party were practically one and the same.

But when Bush and Republicans began to lose power, the antiwar cause also lost prominence. Once Democrats took Congress in 2007, and the White House in 2009, antiwar protests slowly dwindled away, even as Obama and Democrats continued many Bush-era war policies, from expansive government surveillance to drone strikes, and launched new military incursions into Libya and Yemen, among other places. In their book, Party in the Street, Rojas and Heaney blame this on partisanship: The antiwar cause had become so attached to Bush that once Bush was gone, it no longer felt necessary.

For Rojas, this offers another key lesson for movements interested in broader policy changes: “Don’t let your movement become just about party grievances.”

The same applies to Trump, who’s become a galvanizing figure for protesters. But the goals that, for example, the Women’s March seeks to accomplish go far beyond him: Issues like abortion rights, stopping sexual assault, and getting equal pay for equal work are all goals that go beyond one president or political party.

“Donald Trump will not be there for all of history,” Heaney argued. “So if the movement is built as anti-Trump [or] anti-Republican, then when Trump or the Republicans go away, the movement will be dissolved.”

That’s one reason, Heaney explained, that it may be important for the Women’s March to make some inroads with conservatives. Not only could they find enduring allies — many women identity as conservative but find Trump’s behavior or systemic sexism appalling — but they could strengthen their overall credibility by showing their goals and values aren’t solely about partisan interests.

Indeed, the Women’s March has pushed back on suggestions that it’s solely anti-Trump. That’s why, for example, organizers called their actions a rally and march instead of a protest. The idea is to signal not just that Trump is bad for women, but that “women’s rights are human rights.” The movement’s platform doesn’t even mention Trump.

None of this is foolproof. News cycles change. Public attention can fluctuate. Things can suddenly go wrong with no warning whatsoever in any organization.

But if protesters take on the work of building a social movement and succeed, they could quite literally change the course of history.

Watch: Voices from the Women’s March on Washington