I'm not arguing that popularity with the voters is driving this. It's the disdain that Republicans in Washington feel for him. In the Bush and Obama years it wasn't hard to find voters who thought Dubya was a frivolous dumbass party boy whose dad's friends made him president so they could run the country, or that Obama was secretly a brainless bimbo benefiting from a liberal conspiracy to manufacture the illusion of a smart capable black man, but you couldn't find high-ranking members of their own party who voiced that opinion about them or even hinted at it outside of a primary, much less multiple White House sources to confirm it.

Comparing numbers comes with an implicit "all other things being equal..." which is a huge disclaimer in Trump's case. Anyway, his persistent popularity with a certain percentage of the population, far from not penetrating the liberal bubble, is the most famous thing about him. From early in the Republican primary, his opponents have been burned over and over again by assuming that this time his popularity will suffer, this time it's safe to bet against him. I predict that in 2020 there will be more big Republican names ready to bet against Trump.