I must disagree. I think the (R) next to his name accounts for at least 60% of it, however most of that cult of personality which is rooted in politics can be attributed to the Bannon ideology. If Bannon can pull just 10% of that base, which is the hardcore activist volunteering base, Trump’s done.
What do you mean by "pull 10% of that base"? In the primaries, with Bannon challenging Trump? Or are you talking about the general election?
Because on the former, no, an incumbent president is not going to lose re-nomination from his party, barring really extraordinary circumstances. Whoever is the incumbent president becomes a big symbol in the culture war, and it would take a political miracle to pry a critical mass of his party away from him once he's in power. This isn't unique to Trump. Any other incumbent Republican president would be similarly impossible to beat in a primary.