But its effectiveness depends so much on the message I think it's best to think of this as messages (plural) when talking about microtargeting. Everybody could

But its effectiveness depends so much on the message I think it's best to think of this as messages (plural) when talking about microtargeting. Everybody could get a different message but, in aggregate, the set of (Target, Message) tuples could add up to moving the needle towards some desired outcome (for elections, in particular: activating some voters, discouraging others). For example, we might look at the infamous pre-election 2016 meme that cited the fake "Crime Statistics Bureau – San Francisco" and think it's not an effective message because it's so easily disproven. But the real question is whether or not it's an effective message for the subset at which it was aimed. A better phrasing might be "its effectiveness depends so much on the messages in aggregate," maybe.