The gist that I gathered related to arrogance or conceit (such as acting like he's the smartest person in the room), and excessive ambition.
I'm sure that's not how everybody feels, but it is possible that such feelings could be higher than the norm. Certainly the blunt statement made by George W. Bush gives one pause...
Vote Trump
My entire argument was that the original statement was hyperbole - and I proved that to be true.
It is also true that often, those who want to be “the smartest person in the room” dislike the one who actually is. There is no question about Cruz’s brain-wattage, and the examples used: Bush, Boehner, McConnell, etc. are obviously lesser luminaries. And it is very obvious that Boehner and McConnell like to be seen as the smartest person in the room....I am sure Cruz graveled their butts.
Also - his insisting that the gop keep the promises made, generated a LOT of hatred from the standard liars in congress (specifically Boehner and Mitchell).