okay, a couple of things.
One, national polls were only off by 2-3 percentage points. State polls were terrible in WI/MI/PA, states where there wasn't much polling in the final days of the election. So we can trust approval rating polls to be accurate.
Two, yeah this is bad for a president-elect. 40% approvals or lower by 2018 and the midterms will be a bloodbath.
Three, it's not guaranteed to be this bad for Trump forever. He could see higher approvals as time passes.
He will need miracles.
State polls were off badly for the three surprising states that Trump won.
Pennsylvania and Wisconsin were polled frequently, but not often enough at the end.
Trump got a surge in the last few days of the campaign. Polls usually do not show sudden changes.