According to 538, Trump's approval (42.7) was at its highest point since early 2017 on May 7, 2019. It has slipped back to the normal range since (41.4).
I am curious - what was going on the first week of May that led to that run-up? Why didn't it last?
I suspect it has something to do with the Market. The DJIA didn't peak on May 7, 2019, but it had been riding well above 26,000 for a week or two, giving the polls a chance to catch up. Did that cumulatively raise his popularity? The market has fallen a bit since then, as has the approval ratings.
I also suspect that the completion of the Mueller investigation has raised his baseline, and that May 7 was just a normal week-to-week swing from a higher baseline. In other words, I'd take even money that he'll hit or surpass May 7 (42.7) occasionally in the next few months, but fall below it occasionally as well. To the extent his popularity is range bound, I think the range has had a permanent boost.