"Mr. Trump has shifted the Republican coalition toward male votersand less educatedones. At the same time, the party’s advantage among older voters has all but disappeared."
His base voters are white uneducated men over 45 years of age. He won these by very big margins in 2016. This allowed him to win battleground states by very small margins. He has polarised pretty much everyone else. Imo the problem he has is that he has spread himself too thin and won't be able to gain votes from other groups. So, if his voter base shrinks (which I reckon is happening) he will lose battleground states.
