Example letter:

I am writing as a citizen of your district to implore you to do everything in your power to Support and Defend the Constitution of the United States— against all enemies foreign and domestic—and to protect the rule of law in this country.
I am 72 years old and have seen this country go from the Cold War through to today.  It breaks my heart to see our country’s foundation, the Constitution, being shredded.
Please stop the power grab by unelected Elon Musk.
Please protect our valiant patriotic FBI and CIA agents, who are a part of that thin blue line and deserve our protection.
Please work to prevent us from getting into new wars and land grabs.
Please protect my Social Security and Medicare.