I'd like to make a brief point about my own usage. I sometimes use the term "Trumpkin". And I used that as a term of disparagement. That's intentional.
However, I don't use "Trumpkin" as a synonym for Trump voters in general. I don't use it for people who opposed Trump during the primaries, but reluctantly support him in the general election.
There are conservatives who will vote for Trump to block Hillary. It's not so much a vote for Trump as a vote against Hillary. I don't call them Trumpkins.
Rather, I reserve that epithet for Trump primary voters, or for general election voters who minimize his faults, or praise his imaginary virtues. Who make delusional claims about his campaign promises. Things like that.