> aren't we really saying voters are not individual agents but rather a mob subject to manipulation by propaganda?

I invite you to consider the possibility that this is true. That at the population level, propaganda actually works. This would support the fact that it's been a key tool used by regimes (including ours) since before the printing press was invented.

I don't really know for certain whether this is accurate, but it's hard for me to look around the world at global politics and determine that it isn't.