To get out of the mess we're in, ordinary citizens will have to have as much character, vision, and courage as we wish our representatives had. It's every citizen's responsibility to do the hard work of developing his or her own character, vision, and courage. There is no honor in expecting the people we put in office to have more integrity than we do.
If you really want to make a difference, you might try doing the hard personal work of realigning your attitudes and behavior in such a way that they are fully consistent with your stated values.
When most people ask, "But what can I do?" All too often what they are really asking is, "What can I do that won't require me to be uncomfortable or take a risk?" And so they satisfy themselves with making gestures... like writing letters to representatives who have already demonstrated quite clearly that they have neither the courage nor the vision to honor the offices they hold. If they need your letter for advice or courage when it comes to defending the Constitution, then they really don't belong there. Why not use your energy to find and support someone who is really qualified to replace them instead.
It's no wonder that so much political activity and effort makes so little difference to the folks who hold the reigns of power. They are so smug, having absolute faith in our perpetual timidity. The power they hold would belong to us if we had the courage to take it back. All you need to do is believe in the power of the truth ... and then live it.
Sorry, but like I said: The answers are simple; they just aren't easy.
How to protect the Constitution
My Basic Strategy
Win by Losing
An Interview with Jesus