I see "propaganda" on social media of course fairly often. Sometimes I glance at it, and nearly always think, "That won't play at all with the other side, and I don't think it will play for the undecided voters either, so it's a waste of energy." The side that likes it, likes it of course, so maybe it aids turnout. I think a lot of "undecided voters" end up not voting at all, or deciding at the last second based on, well, gravity waves, or write in some name.
Does any of this propaganda and billions in ads impact them? Maybe a few of them, maybe. A lot of it is, to me, poorly done and of course inaccurate anyway. Maybe I miss the "point". I'm personally undecided, and none of it has any impact on me, other than providing some amusement.