Why be subliminal when you can just be obvious?
This is actually a very good point.
Remember, the study on subliminal advertising found that people retained
familiar words and concepts much better and longer than fresh information or novel juxtaposition. So, it's easy to talk people into accepting what they already know, wanting more of what they already want; it's much harder and takes much more repetition, longer, to teach them anything new or get them to change.
But that's already been done, not by what can legally be classified as subliminal messaging, but through the wholly legal, evident and concerted thematic monoculture of the capitalist system.
Commercial advertising, coupled with patriotic jingo in entertainment media, has already trained three generations of Americans to buy whatever they're told is the [currently fashionable] American thing to buy.
Political hustlers get a free ride on that mind-set: they don't need to make up new material; they just take key words from the national mythology and repeat those words, over and over. The candidate who hits the most familiar words most times wins. If they're few enough to fit on a hat, so much the better.
Similarly, the purveyors of junk food (what, there's no bacon crumbs in your milkshake yet? you been livin under a rock?, dangerous drugs (
sideeffectsmayincludedizzinesslowpressureliverdamagestrokeandsuddendeath) financial services to people with no money (borrow more!), vacations (your wife will look 50lb lighter in sandals -- well,
somebody's wife will) just need to rely on the pre-softened heads of their customer base.
They don't need to pay extra for anything clever: stupid works.