Survey research on a mass scale has *never* had great response rates. Trust is certainly part of it, but the main obstacle is the 'foot in the door' moment: convincing people to give researchers an opening to ask questions. The pace of the modern world is increasingly more rapid and pressured, and so (increasingly) people do not want to set aside the time to deal with a researcher, even if it's only minutes. There is too much to do in a day already, and too many easily accessible and enjoyable ways of filling idle time. Survey research is unlikely to be prioritized, unless someone has curiosity about the process or a sense of civic duty that makes them open to the questions.

Once researchers have their foot in the door (so to speak), they have a number of tactics which help them get honest responses. The primary tactic, of course, is institutional reputation. Typically, when someone calls and identifies themselves as a member of a well-known organization — "Hello, Im calling from Pew Research..." — it establishes a level of trust by leveraging the good name of the institution. Unfortunately, since the mid-2000s the more extreme elements of the US Conservative movement have put extraordinary effort into delegitimizing academic, scientific, and political norms and institutions (which did not serve their political agendas). The result is that people on the far Right suffer a trust-gap. I'm sure you've heard people refer to the Right-wing media bubble; that bubble is an expression of that trust-gap, where far-Right conservatives have drawn strong partisan lines about which institution are credible and which are not, a line constantly expanded and reinforced over the last four years by Trump himself (e.g., his 'fake news' and 'lame-stream media' type comments). That by itself should account for most of the 'trust' differences between Republicans and Democrats, since the latter tend to reject that delegitimizing narrative.