The American political system is a democratic republic—citizens elect the people who represent them in government—so public opinion is very important. If political leaders wish to remain in office, they must keep their constituents (and their donors) happy. In order to do this, they need to understand the direction, substance, and intensity of public opinion. For this reason, few politicians make major decisions without consulting polling data in order to ascertain public opinion. However, politicians and interest groups also attempt to shape public opinion. They do this through the use of propaganda and other tools, including, increasingly, social media. This is crucial even for political figures who do not face reelection very often, like the president. Decisions made by the president can have an effect on the popularity of others in their party, like members of Congress, who have shorter terms. Therefore, public opinion matters on an almost daily basis, not just every four years or even every election cycle. Public opinion remains a driving force in American politics.