Washington (CNN) Donald Trump likes to tell everyone how smart he is.

Take Tuesday night in Arizona when he told a crowd in Phoenix this : "I was a good student. I always hear about the elite. You know, the elite. They're elite? I went to better schools than they did. I was a better student than they were."

For the public, Trump's intelligence is a bit more of an open question -- and becoming more open with each passing day in the White House.

Which is interesting. But not nearly as interesting as how rapidly the number of people who think Trump is smart has dropped since November 2016. In a November 22 Quinnipiac poll -- two weeks to the day after the election -- 74% said Trump was "intelligent" while just 21% said he was not.

That number has steadily declined over Trump's first 7 months in office. By March it had dipped into the high 50s and its continued to fall steadily.

Why does it matter?

It might not!

After all, being "intelligent" is not a prerequisite of being President. And intelligence -- who has it and who doesn't -- is a very, very subjective measure. (Do street smarts count as being "intelligent"? Or is it a pure IQ measure? Something in between? Neither?)

And, some of the question about how smart Trump winds up being a proxy for whether or not you like him. Nine in 10 Republicans say Trump is intelligent while just 25% of Democrats say the same. Fifty-five percent of independents say Trump is intelligent.

Still, the numbers -- and the rapid drop in them -- are interesting and telling. Take, for example, the fact that 42% of Democrats said Trump was intelligent in January and only 25% say that now. Or that 70% of independents called Trump "intelligent" in January, but only 55% say so now.

It's impossible to offer a foolproof conclusion that explains those dips.

But, it is absolutely true that in the wake of the 2016 election that even those who disliked Trump also viewed him as a master reader and manipulator of the American public. The default assumption was that he had been -- and would continue to be -- playing three-dimensional chess, and that Democrats would need to up their game to match him,.

It is also beyond doubt that Trump's first 7 months have been marked by chaos -- and an erosion of the belief that he is a strategic mastermind playing a game no one else can possibly understand. As I have written, there's at least as good a possibility that Trump is playing zero-dimensional chess as he is playing the three dimensional kind

Again, being the smartest person in the country -- whether or not Trump is -- isn't how you get elected president. (Sorry, Stephen Hawking!)

But that doesn't make figuring out why Trump's numbers on the "intelligence" question any less fascinating.