A fair amount of research indicates that American politicians aren’t actually all that responsive to public opinion on different issues. The leading interpretation of this is that voters aren’t particularly diligent in monitoring what politicians do. A field experiment from Daniel M. Butler and David W. Nickerson (PDF) indicates that legislator ignorance of what the voters want may be a big deal alongside voter ignorance of what legislators are doing:
When legislators are uninformed about public opinion, does learning constituents’ opinion affect how legislators vote? We conducted a fully randomized field experiment to answer this question. We surveyed 10,690 New Mexicans about the Governor’s spending proposals for a special summer session held in the summer of 2008. District-specific survey results were then shared with a randomly selected half of the legislature. The legislators receiving their district-specific survey results were much more likely to vote in line with constituent opinion than those who did not. Our results suggest that legislators want to be more responsive to public opinion than they are in their natural state and can be if given solid information about constituent beliefs.
It’s not clear, of course, how far this generalizes. But I take it to be another reason why people shouldn’t underrate the merits of writing/calling your members of Congress and state and local representatives. Politicians may be extremely hungry for constituent feedback while lacking the resources to conduct detailed surveys on everything. They’re likely to respond to what they hear.