This double-dealing term came into popular parlance (but mostly online usage) with the unexpected rise, in the early twenty-first century, of Donald Trump as a political force. It has at least two disparate meanings, depending on the user.
Supporters of Donald Trump frequently use it to describe their opponents. To them, it refers to the irrational hostility of people who oppose his policies, statements, or approach to politics.
Those who oppose Trump occasionally use the term to describe their opponents. To them, it refers to the inability of Trump's supporters to acknowledge his dodgy history with business, the law, and alternative facts, and their unwillingness to share the perception that he is not fit for public office.
The term appears to have originated with conservative commentator and columnist Charles Krauthammer, who used the term "Bush Derangement Syndrome" in 2003 to refer to those who opposed the policies and presidency of George W. Bush. His definition was later adopted by Trump supporters. In March of 2025, Senate Republicans in Minnesota introduced a bill to classify Trump Derangement Syndrome as a mental illness. The bill defines the syndrome as the "acute onset of paranoia in otherwise normal persons that is in reaction to the policies and presidencies of President Donald J. Trump." It is not expected to pass.*
No psychiatric body recognizes the "syndrome" and the notion that they should recalls acutely the abuse of psychiatric medicine, in particular, by totalitarian regimes. At present, in American society, it represents a kind of gaslighting by people unwilling to debate political opposition with fact-based arguments. Use of the term also reflects the profound political and social divisions in American society during this time in history.
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Update: On the day that this was posted, police in Minnesota arrested the author of the Trump Derangement Syndrome bill, State Senator Justin Eichorn. He has been charged over allegations that he solicited a teenage girl for sexual purposes.