Out of the blue I got a Quora question this week about a comment of mine from years ago. It was, as usual, a screamingly angry person objecting to my not seeing that Obama was clearly a genius-level IQ. He made the same arguments people usually do that I have seen for years and took care to address in my essay earlier. He seems not to have read that, just the headline. I do not remember my original writing exactly, but I remember the arguments I developed. Simply put, there is good evidence that he has a high IQ in verbal sector (to speak in the more readily known SAT framing), but also evidence that his math abilities are not good. I estimated him at 115-120. That is not far from what most presidents have had, actually. They are usually doers rather than theoretical thinkers and people too far out from the norm - say, over 140 - are often off-putting to enough voters as to be rejected. You don't need to be a genius to be president, just pretty smart. Other qualities are more important.
Speaking of genius, I somehow shut myself off Quora a few years ago and couldn't figure out how to click myself back on. I stopped receiving questions, which I missed at first, but then decided to be grateful for, as it had become an irritating, even infuriating time-suck. I am sure people can explain to me what I did wrong and how to fix it, but please don't. I have already proven that temptation is beyond me, so it is best to just leave the room, leaving my tunic behind.
For the record, we have hard evidence for the IQs of only a few presidents and candidates, the rest we have to estimate, and that always involves speculation. And IQ has only some overlap with wisdom. You need a little of the former to have any of the latter, but after that, other things kick in. Bush 43 tested out just over 125, John Kerry just a point or two less. Al Gore hit 133, and Hillary was a National Merit scholar, and thus at least 139 or so. PJ O'Rourke once did a deeper dive on her thinking and noticed that she had an excellent memory and grasped things quickly, but also leaped to conclusions and seemed to prefer tidy rather than complex answers. That could fit with high IQ, because while those weaknesses are a difficulty, they are more related to personality. It does make her frequent testimony while under investigation, in which she seemed to recall little or nothing, more irritating - though it is a proper legal strategy if you can get away with it.
I moved the dial on my estimate of Trump in both directions when I was writing in 2016. I have not updated. To be a real estate developer requires some facility with big numbers, though it is mostly just arithmetic. To get as much wrong with language as he does is partly personality - not caring what others think - but to be creatively wrong requires some smarts. Yet even that has limits. I had him at ranges of 115-128, which is quite a variance. Bill Clinton was also likely better verbal than math. Bush 41 was probably the smartest recent president or candidate. Jimmy Carter was not a nuclear engineer, as was claimed by some, but he was the chief engineer on a nuclear vessel, which ain't hay. Before that estimates get tougher. Reaching much farther back, the ability to be competent in a range of subjects suggests that Thomas Jefferson and Theodore Roosevelt were likely of high intelligence. A few others showed such facility in writing and composition, even on highly abstract subjects, that they must surely have had sufficient wattage. Madison and John Adams come to mind there.
If one has an agenda about a president it is usually easy to "prove" him stupid or brilliant by carefully selecting the data. Andrew Jackson may have been close to illiterate, so you can paint him a dull gray if you like. Yet he also had such a prodigious memory that when legislation was being discussed, he could recall every previous draft verbatim from what he had heard read out, sometimes over weeks. So bright colors there. It depends what you choose.