Great post :)
I think about this “thirds” thing a lot. I keep returning to Obama’s sky-high approval ratings early on (around 66%) and I think about George W Bush’s second term that spent a lot of time around 33% (though he hit 25% and averaged 37%).
If we think that all people are reachable, it’s hard to explain how W and Trump get even a third. But if we think of them of the bedrock of the GOP base, it makes more sense. They’re compacted. The less popular their leader is, the more firm their support.