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For the second July weekend, President Trump has tweeted offensive slanders about nonwhite Democratic House members who anger him. The latest installment involves claims that Representative Elijah Cummings, chairman of the House Oversight Committee, comes from a district that is a “disgusting, rat and rodent infested mess. If he spent more time in Baltimore,” charged the president, apparently failing to recognize the difference between serving in federal and municipal government, “maybe he could help clean up this very dangerous & filthy place.”

The best explanations for Trump’s actions are often the stupidest ones. Trump has decided the answer to “how I spent my summer vacation” will be sending racist tweets, primarily because that was the thing that he felt like doing at those moments, contradicting the pleas of most of his fellow Republicans.

Yet these impulsive thumb-rants amount to some of the most important and revealing communications of Trump’s presidency. For one thing, they convey the beliefs that have undergirded his career. As Victor Blackwell points out, Trump reserves terms like “infest” and “infestation” — which most people use only to describe diseases or vermin — exclusively for nonwhites. As much hate as he might generate for a target like, say, the mainstream media or transnational institutions, he would never describe the New York Times as an infestation.

Trump’s professional career began in his father’s and his systematically discriminatory housing empire. Excluding African-Americans was the basis of the Trump business model. He did not merely engage in periodic acts of discrimination, but insistently violated federal law and went to war with the Department of Justice rather than amend his ways. Trump’s association of African-Americans with crime and filth, and the assumption they must be cordoned off from other Americans, is a conviction so deep it cannot be uprooted.

As Michael Cohen testified, Trump once commented to him as they drove through a poor Chicago neighborhood, “only the blacks could live like this.” This is a window into to Trump’s obsession with urban blight. It is not a rousing call for better municipal governance curiously misdirected at the wrong branch of government, as he and his supporters tried to suggest in their post-tweet clean-up. It is an expression of his belief that urban poverty is a reflection of black inferiority. He is not proposing, nor do his supporters believe, that having a member of Congress spend more time in his district would meaningfully impact local conditions. He is saying that Cummings is black, the kind of person who would live that way, as a means of discrediting him via his race.

Trump has brought his lifelong patterns of thought with him to the presidency. One of the many oddities of his term in office is that he never observed the traditional break between campaigning and governing, and as a result never adopted even the pose of representing the entire country.

Since he continues to go to war against his enemies in perpetual campaign fashion, and since many of his enemies are domestic, this places Trump in the strange position of frequently disparaging parts of his own country. This is surely unique in American history. American presidents simply do not call American cities filthy and dangerous. George W. Bush may not have enjoyed much support in places like Baltimore, but he wouldn’t go around calling Democratic neighborhoods disgusting hellholes. It does not occur to Trump that the patriotic requirements of his office require representing the whole of it.

It is not merely that Trump is unfit for his job. He refuses, almost literally, to be president of the United States.