If members of Congress are not acting in the interests of their constituents, their constituents have the power to vote them out. The decision not to is what's known as "the consent of the governed". Perhaps that's not exactly the same as "the will of the people" but it's close enough for casual usage.
Some other member from one of the two parties, who will continue to make decisions mostly for their rich donors?
> Princeton University study: Public opinion has “near-zero” impact on U.S. law.
> One thing that does have an influence? Money. While the opinions of the bottom 90% of income earners in America have a “statistically non-significant impact,” economic elites, business interests, and people who can afford lobbyists still carry major influence.
> Public opinion has “near-zero” impact on U.S. law
Re-run that within voting jurisdictions. What that study largely seems to reference is that local representation is, in part, a divide and conquer mechanism.
