People protest against President Trump on Saturday at the entrance to Mar-a-Lago, his resort in Palm Beach, Fla., where he was staying for the weekend. (Joe Raedle/Getty Images)

On Nov. 8, Donald Trump won the presidency with just over 57 percent of Electoral College votes. But as has been repeated often since then, he fell far short of receiving the support of a majority of Americans. He won less than half of the popular vote, and only about half of eligible voters bothered to cast their ballots.

Those upset with Trump’s executive orders and proposed policies know they have company. And in case they had any question about it, the large protests and flood of calls jamming congressional phone lines have put those doubts to rest.

Will these actions and expressions of outrage continue? That hinges on how individual Americans think others feel and what they know about what others will do. Online social networks have made it far easier than was true even a few years ago for individuals to quickly learn about what others plan to do.

In other words, social networks speed up the process of coordination. We believe that will make it easier for the current wave of protests to sustain itself and grow.

What is everyone else doing?

For most people, willingness to do just about anything — whether to wear jeans or go formal, communicate via Twitter or Facebook, protest or stay silent — depends on what they think others will do. As a result, large, highly visible protests, such as the Jan. 22 Women’s March on Washington and the protests against the seven-nation travel ban over the Jan. 28-29 weekend, increase the likelihood that other citizens, even those unlikely to protest, will take other actions to pressure their legislators to oppose White House nominations and proposals.

Economist and Nobel laureate Thomas Schelling used the term “contingent behavior” to describe actions that we take that depend on what we think others will do. Consider a trite example: Do you go to the lunchroom at noon or at 1 p.m.? There isn’t a “right” time for eating lunch — if you’d like company, when you go depends on when you think others will be there. Your decision depends on the information you have about what others will do.

Beliefs about what others will do become even more consequential when choosing between something that’s easy to do and something that takes a lot more effort. If one option is risky, or difficult, or requires more time, then, for most people at least, it’s more likely you’ll do it if your action is coordinated with others.

For instance, consider someone who is opposed to Trump’s executive order on immigration and has to decide what to do on a Saturday night. Should she lie on the couch and watch Netflix — or take the train out to John F. Kennedy International Airport’s Terminal 4 to protest? A great deal of social science research shows that if she thinks she’ll be one of only a few placard holders, she is not likely to bother. The reasoning goes like this: Nothing’s going to change anyway, and I’ll probably feel lonely and even more discouraged, so why not just stay home? She may well believe that pressuring the administration to reverse the order, or urging the courts to consider the action a violation of the rule of law and the Constitution, is more important than watching Netflix. But it also takes a lot more effort, and the payoff is much more uncertain.

Research on so-called “coordination problems” shows that when individuals know others will participate, they are more likely to participate as well. Once someone reads that thousands are on their way to the airport, even the reluctant protester’s sense of which path is more worthwhile flips. Not only does the protest seem more meaningful and potentially effective, but it may also sound more rewarding than scrolling through Netflix looking for a good movie.

(Of course, some people will do what they feel is right regardless of what others do, and the threshold for participation varies widely. Even a few committed individuals can start the ball rolling for a cause that resonates with others.)

Social media activity dramatically speeds up coordination — and helps actions to snowball

Hearing that there are similar protests at airports nationwide can make someone feel like part of a movement. And when someone who hesitated and stayed home during the first wave of immigration order protests learns there were protests in 45 states over 48 hours, he might decide to turn up at the next one. For the same reason, the enormous success of the Women’s March on Washington after Trump’s inauguration probably spurred attendance at the following week’s immigration rallies.

If protest requires common knowledge — a lot of people knowing that many or even most of their peers are also working on behalf of a particular cause — then social media allows dissenters to organize more nimbly and effectively than even a decade ago. Back then, determined organizers needed to call and hold meetings, talk to people, send out emails (and even snail mail) and communicate the results before any action could take place. Those steps moved in real time and cost real money.

Compare that with how protest unfolds today. Over the Jan. 28-29 weekend, social media enabled ostensibly “spontaneous” protests to be invisibly organized via Twitter and Facebook in a matter of hours. Thanks to Twitter, Facebook and Snapchat, Bostonians knew that 20,000 people were planning to go to Copley Square on Sunday afternoon for the second wave of protests. And because those who opposed the order knew that many others were planning to be there, masses did indeed turn out.

With social media, mass sentiment can quickly be communicated — and turned into mass action.

What does this suggest for the weeks and months ahead?

As we have now seen, public responses to controversial actions can snowball, bringing out thousands of peaceful protesters across the United States within hours. Coordinated but independently organized mass protests can take place in real time.

Consider the fact that the next time the White House takes a controversial action, protests can spring up immediately. That means that news outlets will almost simultaneously report not only on the executive action but also on the visible public response.

This changes protest dynamics. If there is mass sentiment, thousands can see, almost immediately, what others think about the new policy. As long as there are determined first movers, a protest can be triggered very quickly, and by historical standards, relatively easily.

The United States may be politically polarized in the extreme. But those who are sufficiently displeased with White House policies will apparently be showing their strength on a scale and at speeds never witnessed in the pre-Twitter era.

Miriam Golden is professor of political science at the University of California at Los Angeles.

Ray Fisman is the Slater family professor in behavioral economics at Boston University.

Together they are coauthors of the forthcoming book, Corruption: What Everyone Needs to Know.