The Illusion of truth
While a proper investigative experiment would need to be designed and carried out to confirm the hypothesis, I believe it is worthwhile to suggest that, in response to the numerous plaintive inquiries in the comments of many posts on Daily Kos as to why Trump supporters believe him when nearly everything that comes out of his mouth is false, the answer can be found on page 62 of Daniel Kahneman's book, Thinking, Fast and Slow (2011) which I quote:
A reliable way to make people believe in falsehoods is frequent repetition because familiarity is not easily distinguished from truth. Authoritarian institutions and marketers have always known this fact. But it was psychologists who discovered that you do not have to repeat the entire statement of a fact or idea to make it appear true. People who were repeatedly exposed to the phrase “the body temperature of a chicken” were more likely to accept as true the statement that “the body temperature of a chicken is 144°” (or any other arbitrary number). The familiarity of one phrase in the statement sufficed to make the whole statement feel familiar, and therefore true. If you cannot remember the source of a statement, and have no way to relate it to other things you know, you have no option but to go with the sense of cognitive ease.
(Cognitive ease being the concept that your mind will naturally go with the easiest option, not necessarily the correct one.) (Italicized emphasis mine.)
We here at Daily Kos all know the lies spread by Trump and the Republican Party. As sometimes slow thinking people (using Kahneman's System 2 reference, not the popular “not smart” understanding) that actually think about what is being said and the underlying premise, if any, upon which the statement rests, we know now the reason for the repetition: to create familiarity and thus the illusion of truth.
Understanding it is the easy part. How do we combat it? The Republicans since the '80s have engaged in this lying operation in order to achieve their ends of political power which allows them to look out solely for No. 1 (themselves and their big money donors). They did so through a systematic effort that started at the local level, getting Republicans elected through promises that – and this I believe is important – at the local level were not necessarily lies. Lies of your township supervisor, mayor, councilman, board member, etc., are not easily made because they are so publicly disprovable: they are, in Kahneman's words, relate-able to other things you know and the dissonance created thereby tells you, “Whoa, Frank is way off base with this! That's just not right and he knows it.” At the local level, you call them out on it in front of the rest of the board, their friends or wherever the setting happens to be.
So at the local level, there likely is not a lot of Republican lying going on but that actually serves a very useful purpose for the up ballot Republicans: it creates familiarity, a willingness to believe what a Republican says at any level. Once you've gotten people to believe their local Republican is telling the truth and is therefore OK, it's easy for the national Republicans to simply say “I'm a Republican...” and whatever follows that can be a lie, the truth, or anything in between. People will believe it because a Republican said it. Contrariwise, when the Republican starts out a comment or a statement with “The Democrats stand for....” people believe what follows is the truth even though it is demonstrably false.
The Democrats need to do the same thing. On steroids. While the Republicans have always been a more disciplined party message-wise than Democrats, it would, I believe, benefit Democrats to adopt the same protocol but with one important difference: tell the truth. Tell the truth all the time, every time. And repeat it, again and again. Tell the American people that “I'm telling you the truth, no matter how ugly and unpleasant it may be, because I believe you are capable of handling the truth.” (References to Nicholson's “You can't handle the truth!” from “A Few Good Men” are optional.) At the same time, draw the distinction – which will be possible in nearly every instance – with the Republican's statements; not the Republican him- or herself, but with what he or she says. Battle the argument and show its falsity without calling the speaker a liar. Those who hear the evidence from those who have told the truth in the past will be familiar with the truth and will conclude the Republican speaker is indeed a liar (without the Democrat having to put the words “liar” and “Republican” together which creates dissonance for the average voter). That person will be more inclined to vote for the one speaking the familiar truth. It sounds ridiculously simple, but I believe it is the recipe for winning.
It will not provide positive results in the immediate future. The Republicans spent 30 years (1980 to 2010) laying the groundwork for their takeover of the government. They've succeeded only to realize that you can't govern – at least effectively or for very long – without telling the truth. But this is a process the Democrats must embrace fully or we, the American people, face the prospect of being ruled by a minority party for the indefinite future. The 2018 elections are too near for this approach to bear fruit; but they can be used to start the process. Given the risks in not taking back the House and at least maintaining (if not increasing) the Democratic Senate seats, whatever truthful policies and statements that can get Democratic turnout maximized must be used along with standard Democratic election methods (GOTV efforts, etc.).
Your Mom was right: honesty is the best policy.