Without his, uh, hardline position on immigration, Trump would be nothing.
In fairness though (even if it's a damn fine line) he could still be as hardline about building the wall and stuff but just cut the parts about "...because they're bringing crime; they're rapists." The insanely hardcore immigration plan isn't itself bigoted and so he could still be by far the most out there candidate on the issue and pick up a similarly solid segment of people for whom that is the, or close to the, number one issue.