As requested...
I could be mistaken, but I seem to remember him being more supportive of Democrats than Republicans, more liberal than conservative... Considering all of Hillary's lies, could it be she converted him to the Never Hillary camp?
If he said it, what makes you think he was referring to Democrats?
[edit]
It appears that he tweeted this in 2013. The question stands. I don't see the quote as referring to one party or the other.