What is meant by the term ‘issue public’ as described in the excerpt?

In my observations of this great and evolving democracy, I have noted that not every matter impacting the populace commands equal attention from all citizens. There exists a distinct division wherein certain issues, though not resonating broadly, ignite fervent concern among a dedicated minority. This select group, often referred to as the ‘issue public,’ invests disproportionate energy into causes that may lack widespread appeal. Such concentrated enthusiasm, despite its limited scope, frequently influences policymakers in unexpected ways. At times, the intensity of focus by this minority can elevate a seemingly peripheral matter to a position of national debate. In these cases, the voice of a small segment can shape the discourse of public policy with remarkable effectiveness.

Alexis de Tocqueville, Democracy in America: Reflections, 1835