The election of Donald Trump has brought new people into politics and re-ignited activists. As people on the left aim to resist what they view as Trump’s dangerous and harmful policies, and people on the right try to sustain political engagement after the election, both sides are debating about the effectiveness of various political strategies. For example, Indivisible, a guide compiled by Congressional staffers on tactics for opposing President Trump, spread quickly across the internet as people grappled with how to effectively influence policy-making.

Contacting legislators is one of the most common forms of political engagement in the United States. Hearing from constituents, particularly in face-to-face meetings and phone calls, can influence politicians’ action on an issue. The greatest impact, however, is when the contact is outside of routine communications and part of a collective campaign. Social scientists have found that politicians are more likely to react to new information that indicates a change in the political landscape and ties their stance to their electability. An organized effort can demonstrate that a group has powerful resources, such as volunteers and donations, which in turn can affect politicians’ ability to get re-elected.

Legislators are not always just responding to public opinion either. They are also influenced by lobbyists, political donations, personal political views, and party platforms. Nevertheless, popular opinion may play a larger role in shaping elected officials’ positions when it signals a dramatic shift and the public feels strongly on one side of an issue. Thus, political organizations and concerned citizens can influence policy by raising and changing public awareness, and then explaining these popular sentiments to politicians who learn about their constituents attitudes.

The effectiveness of contacting politicians also depends partially on the party and race of the official and the constituent. People are more likely to contact a politician from their own political party, so contacting leaders outside of one’s own party disrupts political norms — which is sometimes effective and sometimes discounted. The response of elected officials to the public is also shaped by racism. For example, a real-world experiment found that white legislators discriminate against emails and calls from black constituents.