MOLLIE HEMINGWAY NAILS IT:

Trump and his campaign are perfectly positioned to exploit every weakness we have in the electorate. If the Republican Party didn’t want to have this opposition, they should have picked literally any type of policy and just made it happen, even as late as last summer. If voters could have seen that the Republican Party was capable of doing something big and dramatic, and communicated that to the people, I don’t think that you would have had the hunger to blow up the system like with the Trump movement.

If they’d had just one otherwise-acceptable candidate who wasn’t an open-borders type, they’d have been immunized against Trump. But they couldn’t allow that.