Anthony Downs

“From these definitions and axioms springs my central hypothesis: political parties in a democracy formulate policy strictly as a means of gaining votes. They do not seek to gain office in order to carry out certain preconceived policies or to serve any particular interest groups; rather they formulate policies and serve interest groups in order to gain office. Thus their social function—which is to formulate and carry out policies when in power as the government—is accomplished as a by-product of their private motive—which is to attain the income, power, and prestige of being in office.

This hypothesis implies that, in a democracy, the government always acts so as to maximize the number of votes it will receive. In effect, it is an entrepreneur selling policies for votes instead of products for money. Furthermore, it must compete for votes with other parties, just as two or more oligopolists compete for sales in a market.”
― Anthony Downs, Theories of Democracy: A Reader