Trump Plucked The Populist Apple
Take a look at the 2005 Political Typology report by the Pew Center. Note well that this came out over a decade ago. That is, before the economic crash of 2007-08, and before disillusionment with the Iraq War and the Bush administration had taken hold.
Here are the relevant takeaways:
A total of 46 percent of registered voters — Republicans and Republican-leaning independent — had in 2005 a political profile that fits with the Trump brand.