Many observers seem baffled by Republican fealty to Donald Trump — the party’s willingness to back him on all fronts, even after severe defeats in the midterm elections. What kind of party would show such support for a leader who is not only evidently corrupt and seemingly in the pocket of foreign dictators, but also routinely denies facts and tries to criminalize anyone who points them out?

The answer is, the kind of the party that, long before Trump came on the scene, committed itself to denying the facts on climate change and criminalizing the scientists reporting those facts.

The GOP wasn’t always an anti-environment, anti-science party. George H.W. Bush introduced the cap-and-trade program that largely controlled the problem of acid rain. As late as 2008, John McCain called for a similar program to limit emissions of the greenhouse gases that cause global warming.

But McCain’s party was already well along in the process of becoming what it is today — a party that is not only completely dominated by climate deniers, but is hostile to science in general, that demonizes and tries to destroy scientists who challenge its dogma.

Trump fits in with this mindset. In fact, when you review the history of Republican climate denial, it looks a lot like Trumpism.

Take Trump’s dismissal of all negative information about his actions and their consequences as either fake news invented by hostile media or the products of a sinister “deep state.” That kind of conspiracy theorizing has long been standard practice among climate deniers, who began calling the evidence for global warming — evidence that has convinced 97 percent of climate scientists — a “gigantic hoax” 15 years ago.

What was the evidence for this vast conspiracy? A lot of it rested on, you guessed it, hacked emails. The credulousness of all too many journalists about the supposed misconduct revealed by “Climategate,” a pseudo-scandal that relied on selective, out-of-context quotes from emails at a British university, prefigured the disastrous media handling of hacked Democratic emails in 2016.

The truth is that most prominent climate deniers are basically paid to take that position, receiving large amounts of money from fossil-fuel companies. But after the release of the recent National Climate Assessment detailing the damage we can expect from global warming, a parade of Republicans went on TV to declare that scientists were saying these things only “for the money.” Projection much?

Climate scientists have faced harassment and threats, up to and including death threats, for years. And they’ve also faced efforts by politicians to, in effect, criminalize their work. Most famously, Michael E. Mann, creator of the famous “hockey stick” graph, was for years the target of an anti-climate science jihad by Ken Cuccinelli, at the time Virginia’s attorney general.

If we fail to meet the challenge of climate change, with catastrophic results — which seems all too likely — it won’t be the result of an innocent failure to understand what was at stake. It will, instead, be a disaster brought on by corruption, willful ignorance, conspiracy theorizing and intimidation.

We can now see climate denial as part of a broader moral rot. Trump isn’t an aberration, he’s the culmination of where his party has been going for years. You could say that Trumpism is just the application of the depravity of climate denial to every aspect of politics. And there’s no end to the depravity in sight.