Mainly through political parties and the media platforms on which they argue.
The chapter's answer is that parties do not only fight elections — between elections they organise public opinion and campaign on specific issues (Fig. 7.9). When a party takes up a question of price, employment, schooling, water or safety, it turns a private difficulty that many households face separately into a public issue that has to be answered in the legislature. The chapter adds that parties "discuss and debate on issues of local, state, national, and international concern through various media platforms" — so newspapers, television and the internet carry the argument to citizens who were never at the rally.