Trump was the worst possible Republican for WI and he still won the state. The Midwest is an area where Trump has a lot of room to grow - unlike FL or NH, for example. Granted, no one knows for sure whether he will do better in the WOW counties, Philly suburbs, rural MN, etc. in 2020, but at least it's possible.
And no, I don't think every state that was within 10 points should be considered competitive. No one would consider states like Virginia and Colorado to be in play, for example.
-Trump was definitely
not the worst possible Republican for WI: in fact, he was probably the best. Cruz (like Romney; see the primaries both in 2016 and 2012) had little appeal outside the eastern part of the state, while the people Trump won in western Wisconsin in the primary did not tend to be party-hack types at all, and many voted for Barry O in 2012. The people who Cruz won in the 2016 primary were definitely party-hack types, and were generally the same people Romney won in the 2012 primary. That didn't help Romney in November, and it wouldn't have helped Cruz, either. Trump alienating a tiny number of Cruz-supporting party hack types (less than 2%) while gaining very many Obama voters in western Wisconsin definitely made him a very strong candidate for the state, certainly stronger than Cruz, who would have kept all the party hack types, but would have been unable to appeal to Obama voters.
Rubio would likely have won VA and CO in November if Trump was the Democratic nominee and Rubio was the Republican. They're still winnable, but only by a certain type of Republican, and only in a situation of low minority turnout. Trump was never likely to win them; he was a very bad candidate for both states.
