It HAS???
How do you 'know' this?
I am not here to defend polls, I am simply here to tell you that professional politicians take polls very seriously, foreign governments judge the power of the American president on the basis of these polls, and no one but no one takes his polls more personally and more seriously than does Donald Trump himself.
I am not going to argue whether these polls are accurate or not. Make up your own mind. If you think they are problem then the question becomes what to do about it. If you think they are problem but you do not know what to do, you could always attack me, that should make you feel better.
But if you do want to feel better for God sake do not think about Trump's conversations with the premier of China when that man knows that Trump's approval ratings are in the 30s.