It’s quite simple.
CNN is strongly anti-Trump, and has a long history of “inventing” news as it suits them.
I am not familiar with Rasmussen, but am quite open to believe hat they are equally biased, in the other direction.
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If you want honest polls of the American political situation, you need to ask someone that does not have an axe to grind… I.E. You need someone that is not themselves pro- or anti-Trump, and is also not under influence from the American leadership.
Heh. Good luck with that!