When I was an undergraduate student, I took my Social Psychology course through my university's Sociology Department. My professor at the time enjoyed introducing us to cognitive dissonance theory, and one of the field observations of a doomsday cult that Festinger and colleagues documented in their book, When Prophecy Fails. Although the methodology behind the observations that made up the core of that book are not above criticism, it remains a valuable document for understanding cults of any sort, including those of a more political nature.
Cognitive dissonance theory is itself fairly straightforward. One has a strongly-held belief. It may be challenged either by a belief-inconsistent behavior the individual performs (a common thread in a lot of lab experiments) or an inconsistent external event. That creates considerable psychological tension (think of anxiety, for example) and is resolved by either modifying one's beliefs or doubling down and continuing to believe. In the case of the doomsday cult that Festinger and colleagues followed, the world did not end, many of the members remained, believing that the power of their faith had spared the planet.
The author of a recent article in The Atlantic, McCay Coppins, uses the book and the theory as means of understanding at least a certain subset of the modern GOP that appears to have truly bought in to what has become known as Trumpism. He covers an event on election night that includes such Trump luminaries as Steve Bannon. The event itself was celebratory at first, but as the night wore one, it became apparent that the narrative of the polls being fake (rather than being merely imperfect, as they typically are), that a Trump landslide was forthcoming, etc., was not going to hold up. The mood of the attendees and of its host certainly changed (we could probably throw in some frustration-aggression theory in as well). But at minimum, this inconvenient truth that Biden was going to prevail in not only the popular vote (which means little in the US) but also in the electoral vote was enough to cause the proverbial house of cards to fall. In the moment, that was met by bitter denials by an event host. We've seen since increasingly shrill denials and actions held at various locations where those workers responsible for counting ballots, along with poll watchers, do their tedious work. So far, it appears that at least a subset of our population does not believe what the data are showing, and are bound and determined not to believe it. When dissonance hits, the defense mechanism of denial seems to be the impulse. We saw that most recently at a hastily convened press conference on the outskirts of Philadelphia, at a landscaping facility located near a crematorium and an adult bookstore. But we've also seen true believers show up in Las Vegas to invoke their deity at the Clark County Election Department, and regular armed protests at the Maricopa County Election Department in Arizona. In this particular psychological space, Trump is portrayed as the legitimate authority whose position is being "stolen" for....reasons.
The election will eventually be certified (after some remaining lawsuits and transitional roadblocks are dealt with), and a transition to a new administration will happen. That is reality, based on the votes counted, and based on what is known of the likely votes remaining. However, that reality will not be accepted by a significant subset of the US population. It may never be accepted. We don't know yet. But for now, the resolution to cognitive dissonance appears to be denial.