They're not reading every constituent message, many reps get thousands of messages a day. But they're seeing aggregated reports. If a rep suddenly starts getti

They're not reading every constituent message, many reps get thousands of messages a day. But they're seeing aggregated reports. If a rep suddenly starts getting a thousand messages a day all supporting/opposing issue X, that's going to get noticed. Generally a handful of messages is fruitless, but a persistent big batch can change policies, especially if it's between multiple alternatives the member is already OK with.