I guess you must know a saying about the advertisement :
You can cheat for a small number of people, or you can cheat in a short period of time, but
"YOU CAN NEVER CHEAT A LARGE NUMBER OF PEOPLE FOR A LONG TIME"......
In some cases, what you said might be right and many politicians take advantage of propaganda to manipulate their people by fancy advertisement on social media at all in their countries, but the truth is hardly to be hidden for a long time. More and many people would know the truth years after. But of course, some people who were sacrificed or killed then can never relive and come to their families, which is pretty sad.
There is another issue to be considered: How is the totalitarian party produced, encouraged or boosted? It is more than likely that most of the citizens who have the right to vote unintentionally indulge their acts and obviously in such an instance hardly can you say voters are totally able to exempt from their obligation in identifying the right politicians.
It goes without saying this is meant to be a complicated issue and seemingly hard to be simplified as several sentences.