Trump won with thin margins in a handful of states that handed him a clear majority in the Electoral college, while losing the overall popular vote by almost 3 million. If Hillary Clinton had been a little more popular, or had put more effort in states like Wisconsin, she would have ben president.

Obama had a reasonably high approval rating as an outgoing president. It's just an educated guess, but I think Obama would have beaten Trump in any year, and probably with better margins than he beat McCain or Romney.

"Domestic failure" is in the eye of the beholder, and I don't live in the country myself. All I know is that public approval of the Affordable Care Act has been going up ever since the Republican party has been in a position to actually undo it.