It's actually quite clever/sinister. Suggests they've got behavioural scientists or similar working on their social media content.
Changing the one word doesn't alter the way our subconscious perceives the message. There's also the word association thing going on. What it does do is massively increase the number of people who see it, as people share and discuss it (as has happened here).
The repetition of a message has been shown to have a positive effect on people's reception and agreement with said message, independent on whether it actually has any substance. Obvs on this thread, most people already hate Johnson so it won't move the needle much, if at all. But it will have an effect on some people's psychology, as that phrase will be repeated constantly until the next election. Similar to Get Brexit Done, it'll literally be the only thing some people base their votes on, as depressing as that is.