These national polls are rather meaningless w.r.t. the election.
Trump doesn’t need a single vote in California or New York to be re-elected.
It will come down to who can win swing states such as Wisconsin, Michigan, Pennsylvania, Florida, etc. I suspect the Democrats will ultimately select a nominee that is farther left than Hillary was, and Trump will have another popular vote loss, but easy electoral victory. (I also expect the Republicans will hold the senate, and Dems will hold the House.)