I find it hard to believe he's just barely underwater in a state that voted for Hillary. Probably best to take that poll with a grain of salt.
EDIT: Hmm, now that I'm taking a closer look at the crosstabs, does it really make sense that he's only down by 2 points overall when he's doing about as badly with Democrats as he is doing well with Republicans, and is down 13 points with unaffiliateds? I'm thinking their sampling distribution might just be off.
Magellan has always had an R bias, although not a huge one. I think the key factor in this result is:
If this was weighted to match turnout demographics from past midterms, it may be more R-friendly than 2018 is likely to be. Something that supports this idea: they have Congressional approval at 34-58. Although underwater, this is still much friendlier to Congress than recent national polls.