During a speech in Cincinnati, Mr Trump suggested Democrats were "un-American" because they did not full-throatedly embrace his address to a joint session of Congress last week.
"They would rather see Trump do badly, okay, than our country do well," he said."It's very selfish. And it got to a point where I really didn't even want to look."
"They were like death and un-American. Un-American. Somebody said, 'treasonous.' I mean, yeah, I guess, why not?"
"Can we call that treason? Why not? I mean, they certainly didn't seem to love our country very much," he added.
But Nielsen ratings show that three of Mr Trump's predecessors surpassed his audience numbers during their first time giving the high-profile speech before Congress.
Mr Trump did see a slight bump in the polls however, with his Gallup approval rating edging up two points to 40%, its highest level in months.