It is unreasonable to say in one breathe that politicians are self-interested, but then to say that your voice carries no weight. A great example is the very competitive Senate race in Montana. Incumbent Senator Tester supports Elizabeth Warren's bill. But in this close race, softly held beliefs are easily tested. If you live in Montana, call you Senator and let him know what you think of Warren's Digital Asset Anti-Money Laundering Act.
And if you think vulnerable incumbents aren't flexible, take a gander at this.