To many observers on the left, the initial embrace of Seth Rich conspiracy theories by conservative media figures was merely a confirmation of the right’s deformed soul. But for those of us who remember that Rush Limbaugh and Sean Hannity were once relatively mainstream Reaganites, their extended vacation in the fever swamps is even more disturbing. If once you knew better, the indictment is deeper.

The cruel exploitation of the memory of Rich, a Democratic National Committee staffer who was shot dead last summer, was horrifying and clarifying. The Hannity right, without evidence, accused Rich rather than the Russians of leaking damaging DNC emails. In doing so, it has proved its willingness to credit anything — no matter how obviously deceptive or toxic — to defend President Trump and harm his opponents. Even if it means becoming a megaphone for Russian influence.

The basic, human questions are simple. How could conservative media figures not have felt — felt in their hearts and bones — the God-awful ickiness of it? How did the genes of generosity and simple humanity get turned off? Is this insensibility the risk of prolonged exposure to our radioactive political culture? If so, all of us should stand back a moment and tend to the health of our revulsion.

But this failure of decency is also politically symbolic. Who is the politician who legitimized conspiracy thinking at the highest level? Who raised the possibility that Ted Cruz’s father might have been involved in the assassination of John F. Kennedy? Who hinted that Hillary Clinton might have been involved in the death of Vince Foster, or that unnamed liberals might have killed Justice Antonin Scalia? Who not only questioned President Barack Obama’s birth certificate, but raised the prospect of the murder of a Hawaiian state official in a coverup? “How amazing,” Trump tweeted in 2013, “the State Health Director who verified copies of Obama’s ‘birth certificate’ died in plane crash today. All others lived.”

We have a president charged with maintaining public health who asserts that the vaccination schedule is a dangerous scam of greedy doctors. We have a president charged with representing all Americans who has falsely accused thousands of Muslims of celebrating in the streets following the 9/11 attacks.

(Claritza Jimenez/The Washington Post)

In this mental environment, alleging a Rich-related conspiracy was predictable. This is a concrete example of the mainstreaming of destructive craziness.

Those conservatives who believe that the confirmation of Justice Neil M. Gorsuch is sufficient justification for the Trump presidency are ignoring Trump’s psychic and moral destruction of the conservative movement and the Republican Party. Clinton, with a small number of changed votes, would have defeated Republicans. But Trump is doing a kind of harm beyond anything Clinton could have done. He is changing the party’s most basic moral and political orientations. He is shaping conservatism in his image and ensuring an eventual defeat more complete, and an eventual exile more prolonged, than Democrats could have dreamed.

The conservative mind, in some very visible cases, has become diseased. The movement has been seized by a kind of discrediting madness, in which conspiracy delusions figure prominently. Institutions and individuals that once served an important ideological role, providing a balance to media bias, are discrediting themselves in crucial ways. With the blessings of a president, they have abandoned the normal constraints of reason and compassion. They have allowed political polarization to reach their hearts, and harden them. They have allowed polarization to dominate their minds, and empty them.

Conspiracy theories often involve a kind of dehumanization. Human tragedy is made secondary — something to be exploited rather than mourned. The narrative of conspiracy takes precedence over the meaning of a life and the suffering of a family. A human being is made into an ideological prop and used on someone else’s stage. As the Rich family has attested, the pain inflicted is quite real.

A conspiratorial approach to politics is fully consistent with other forms of dehumanization — of migrants, refugees and “the other” more generally. Men and women are reduced to types and presented as threats. They also become props in an ideological drama. They are presented as representatives of a plot involving invasion and infiltration, rather than being viewed as individuals seeking opportunity or fleeing oppression and violence. This also involves callousness, cruelty and conspiracy thinking.

In Trump’s political world, this project of dehumanization is far along. The future of conservatism now depends on its capacity for revulsion. And it is not at all clear whether this capacity still exists.

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