That's both factually and mathematically incorrect. Trump only won pluralities in most of the Primaries and many of them were open so independents and registered Dems could vote. 

Second, we live in a Republic, where political power is deliberately dispersed vertically and horizontally at every level. Trump is running for a single position. He may be the defacto -face- of the Party as far as media coverage goes, but he doesn't -represent- more than the bare pluralities that got him the nom. As shown by the fight to free the delegates and the decision by many Party leaders to not endorse him.