A lot of people who have experienced it as a tactic of emotional abuse react negatively to applying the term "gaslighting" to politics, but this Jamelle Bouie article about the VP debate makes a convincing case that it is the best description for one of the Trump campaign's main strategies and, in the future, most toxic legacy.
I've been in two relationships where this has happened to me. It hits me hard and in an exaggeratedly personal way when I see this happen in a political context. As a tactic, there's no doubt that it works. After weeks and months of being told that you're crazy, that you're imagining things, that things that happened did not happen, that things that were said were not said…it's not much of a leap to questioning your own sanity and perception. And it's not easy to bounce back from, either. It has been several years since I got away from it and I'm not completely over thinking that way. The way I hold onto things, there's a decent chance I'll never be completely over it.
Only very rarely do I write about even the most trivial personal matters on here, so it feels very uncomfortable to throw this out there. But I bring it up to underscore the viscerally negative reaction I have to watching Trump and Pence use a calculated strategy of lying blatantly and assuming – correctly, in most cases – that Americans are too lazy, too uninterested, or too short of attention span to remember to check their statements for accuracy. There is no other explanation for why a candidate would repeatedly insist "I/he never said that" when it is so remarkably easy to verify in this day and age that it was in fact said. Hillary Clinton's campaign, just for example, had videos of Trump saying many of the things Pence asserted he never said circulating online before the debate even concluded.
To formulate a campaign strategy around a technique of abuse and manipulation says a lot about the kind of human beings we are dealing with here. Politics has always treated the truth somewhat casually. Interpretations of facts, statements, and events are often creative to say the least. But simply to insist that a verifiable fact, statement, or event is not true or did not happen is rarer than our cynical view on politics might conclude. Imagine if George H.W. Bush had campaigned in 1992 insisting that he never said "Read my lips" or if Bill Clinton continued to insist that he had no "sexual relations with that woman" even after evidence was brought to light that it did. People lie a lot in politics, but rarely do they continue to perpetuate a lie that can be so easily disproved.
It takes a remarkable amount of gall to do that on a worldwide television broadcast. Or it takes a total lack of respect for the dupes you perceive to be watching. Or it takes being a fundamentally abusive, manipulative, narcissistic person. The Venn Diagram of those three circles has Trump and Pence in the middle.