A good argument can be made is that Trump is a traditional Democrats in the mold of people such as John Kennedy, Lyndon Johnson and Franklin Roosevelt, whereas the Democrats have moved radically to the left and are now support positions that in the past would have been considered off-the wall radical. If we had proportional representation, we could accomodate more parties but we have a “winner takes all” system. Note that in periods where the Republicans were dominated by conservatives, Trump was a Democrat.
His nativism and his pungnacious campaign style really don’t reflect his ideological background or his substance. In terms of issues, he’s either a conservative Democrat or a liberal Republican.