That's what the mass media, which is skewed to the left, wants you to think. The truth is that his approval rating is doing okay, and it's especially good for republican voters.
This is true, but maybe not for the reasons you think. The number of people who self-identify as "Republican" has shrunk considerably over the past few years. https://www.brookings.edu/blog/fixgov/2018/06/14/trump-owns-...
Yes, Trump's approval rating is dead average for President’s taking office after the end of Obama’s second term at the same point in their term of office.
But unless you reduce the domain so much that you compare Trump only to himself, it's not perfectly normal.