Well, it's because of his wonderful military leadership...no wait, he ducked out of the White House during Benghazi and left everything up to Hillary and to deal with.
OK, well it's his wonderful job of fixing the economy...no wait, his budgets that were sent to congress never even got a Democrat vote, all he does is complain that Congress doesn't do their job. Can't touch him there.
I know, all of the promises he made on immigration, Guantánamo, jobs, lower gas prices.....ok never mind.
Other then the fact that the majority of his supports are low-information voters I don't have a clue.