Uh, I’d say “vote Democrat” here too. Democrat is the noun, Democratic is the adjectival.
In the sentence “Voted Democrat down ballot,” Democrat is acting as a noun. Now if they had said “Voted for Democrat candidates down ballot,” you’d have more of a point.
Democratic administration sounds more correct than Democrat administration unless you’re severely Fox News brained. I haven’t ever heard anyone calling it a “Republic administration” which would sound just as wrong (and the wrongness is absolutely intentional IMO).
Yes, Democratic Administration makes sense, because “Democratic” is acting as an adjective to “Administration”. In this example you do want to use Democratic.
But “Voted Democrat down ballot” still sounds fine to me.
The administration thing is what I thought was a clear Republican talking point indicator. It got a little muddled what I was talking about so sorry bout that.