How are political parties forced to serve the people even if they are not interested?

(i) If a political par-ty is motivated only by desire to be in power, even then it will be forced to serve the people.
(ii) It is how a market works. Even if a shopkeeper is interested only in his profit, he is forced to give good service to the customers. If he doesn’t, the customer will go to some other shop’
(iii) Similarly, political competition may cause divisions and some ugliness, but it finally helps to force political parties and leaders to serve the people.