Psychologists Lynn Hasher, David Goldstein, and Thomas Toppino named the illusory truth effect in 1977. According to this cognitive bias, people tend to perceive information they have heard repeatedly as more true and reliable than information they receive for the first time. In other words, repetition is an effective tool of persuasion: it makes a message gain credibility through the act of hearing it. That said, I do not know if our politicians have ever studied the illusory truth effect, but they certainly master it to perfection, even if only intuitively.