A large swathe of American conservatism now bears a closer resemblance to a fundamentalist religious movement than a broad-based, essentially pragmatic political party.
People with closed minds want their convictions reinforced rather than tested, so they restrict their sources of information. That inevitably exposes them to more extreme views and shields them from counter-arguments and facts which don't square with their beliefs.
There's the fact that the conservative political establishment has, for perceived, narrow, short-term gain, taken partisanship to a new level. Not content simply to oppose Barack Obama, Republicans in Congress and state governments have tried to delegitimise him by portraying him as unAmerican, personally and philosophically.
Hence the Birther movement which maintains, despite documentary evidence to the contrary, that Obama wasn't born in the USA and therefore isn't eligible to be president. Trump has been Birtherism's most prominent and vocal adherent.
There's distrust of the primary source of objective truth, the mainstream news media, largely as a result of years of accusations of liberal bias. The mainstream media's commitment to even-handedness compounds the problem: it treats the two major parties the same even though one has largely abandoned traditional, consensus-based politics and no longer plays by the rules.
The media take a "politics as usual" approach to lying, although it's abundantly clear Trump and co have upped the ante. The Pulitzer Prize-winning fact-checking organisation PolitiFact has found that 41 per cent of Trump's statements are false and 21 per cent fall into the most egregious category of falsehood, while Carson comes in at 46 per cent false and 13 per cent egregious. Democrat frontrunner Hillary Clinton, hardly a byword for fastidiousness in this regard, scores 11 per cent and 1 per cent.
The broad left isn't blameless. Through its kneejerk moral relativism and enthusiasm for intellectual fads such as post-structuralism, the intelligentsia has flirted with the notion that there's no such thing as objective truth, while that liberal hotbed Hollywood has long pandered to American paranoia.
Interestingly, the most glaring example of US citizens having good cause to distrust a state agency - the black community's fear and loathing of the police - has precious little support on the populist right.
Are we witnessing the death of objective truth? No. The fact that it survived the propaganda, brain-washing and personality cults of 20th century militarised totalitarianism shows how strong mankind's yearning for the truth is.
And while Trump may have borrowed from Hitler's playbook, he's not a Nazi. As Walter says in The Big Lebowski, "Say what you like about the tenets of National Socialism, but at least it's an ethos." There's no Trump ethos; there's only Trump ego.