You do realize Donald Trump was registered Democrat from 2001-2009? Sorry, but that excuse isn’t going to pass muster.
We know that the Donald was registered Republican beginning sometime in the 1980s. I am not aware that we know his registration prior to that. But we do know that he and his father were in close with the Brooklyn Democratic Party and, in particular, Mayor Abraham Beame. This is how I have him meandering D to R to I to D and then back to R.