Take a good look at the primary results for Trump. He has been the accepted nominee in his party for several weeks. All his opponents have explicitly left the field and suspended their campaigns. The national party recognizes Trump as the nominee; the media do as well.
And yet! And yet! In all six states anywhere from one-fifth to one-third of the die hard Republican base, the ones who do vote in primaries and are likely to be the ground workers who give money, who knock on doors, who phone bank — a fifth to a third of them hate Trump so much that even knowing he is the nominee, they come out and vote — against him.
They give up an hour or several hours out of their day. They walk or drive to reach the polling place. They doggedly ask for a ballot and mark it, knowing it will not change the outcome, but they want to go on record, even if it is only the private record of their hearts: I did not vote for this man!
In some ways, I feel sorry for them.