I like to follow the RCP aggregate poll graph:
The current shutdown started Dec 22. It usually takes polls about a week to catch up with the news (they are reported by RCP after they are completed)
If one looks at the Trump disapproval line starting Dec 30 to date, there is a pretty unavoidable conclusion - the disapproval line is trending up at a steep angle. My takeaway conclusion is that the shutdown is really hurting Trump’s approval rating, and we have yet to see any tapering off. Time will tell - we’ll have to see if his disapproval in this aggregate of polls beats the former high of 58.1% reached Dec 14, 2017.