After writing that McCain is RINO-in-Chief, it occurred to me I should answer the question "Why doesn't Rand Paul (R-KY) deserve the title even more?" You could fairly make that argument, here's my reasoning.
McCain claims to be a real Republican, but rarely acts like one. Rand Paul, like his dad Ron Paul, is in fact a Libertarian who, like Socialist Bernie Sanders across the aisle, lines up with one of the two major parties out of convenience.
Paul doesn't claim to be a 'real' Republican, but is rather an individual who wishes all Republicans would become Libertarians (while knowing they won't). Sanders, on the other hand, appears to be getting his wish that many Democrats move to the left and embrace socialism.
And, yes, I excuse the squishiness of Susan Collins (R-ME) and Lisa Murkowski (R-AK) as part of the difficulty women have with the Republican Party's bedrock policy of "tough love." We've written before about Rs being the "daddy" party and Ds being the "mommy" party.
As this society raises people, tough love comes easier to guys than to gals, easier to daddies than to mommies. Personally, I'm okay with that division of labor, I fully understand if you find it distasteful.
Later ... On the other hand, I will support (editorially) realistic primary challenges to any or all of these four defectors by men or women who embrace the Party's "tough love" policy and support its POTUS.