No, Donald Trump did not say he would run as a Republican because "they are dumb" (or any variation of that sentiment). This is a longstanding hoax that originated around 2015 as a viral meme falsely attributing a 1998 People magazine interview to Trump. The fabricated quote reads: "If I were to run, I’d run as a Republican. They’re the dumbest group of voters in the country. They believe anything on Fox News. I could lie and they’d still eat it up. I bet my numbers would be terrific."