How does popular opinion shape political policies? Mccarthyism

Political policies are indirectly a product of the public opinion. Any democracy elects the nominees as a representative who would cater to their needs and who work for a better and more developed society and living conditions. The political parties are there to formulate and execute public policies that would govern the people and the country itself. The public opinion is the one ingredient that is crucial to shape these policies. For instance, an educational policy will highly depend on the present need and the condition of the education system, the analysis of which would be closer to the reality only if based on public opinion. And hence political policies are shaped by popular opinions.