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.
Huh! The Brooking's story actually cites this Gallup data. But it's a little out of date. Looks like Republican ID has sprung back up in the last ~6 months. Touché!
It's really noisy poll-to-poll; really, I'd be skeptical of anyone claiming that there is much of a meaningful trend based on it. Pew’s series which separately tracks partisans and leaners might be more useful for spotting trends, but they do take seem to have really recent data public in that series.
> I think it's perfectly normal given how politics works now.
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.
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-...