What that suspicion and cynicism produce is a huddling effect among partisans. Convinced that the honest brokers simply don’t exist, they tend to seek political sustenance from those who affirm their points of view. They watch the same TV shows, listen to the same radio stations, shop at the same places and live in the same neighborhoods as people who believe like they do. Interactions with people with which they disagree and entities like Congress or the news media dwindle.
Among people loosely or not-at-all aligned with a major political party, the erosion of confidence in institutions leads to a sort of throwing up of the hands and a disinterest, broadly, in what government and politics can (or will do) in their lives. Why care about Congress if you don’t trust in their motives? Same goes for the news industry.
The declining belief in institutions is — surprise, surprise — a very difficult reality with which politicians (and the broader world of government) have to grapple. How do you get people to vote for you who simply don’t believe you know or want to do the right thing for the country? How do you get people to read you if they think you are pushing an agenda? How do you get the public to follow your legal decisions if they are skeptical of why you made it?