That link doesn't really support your claim, and their own claims are poorly supported by their assertions anyways. First, they show that Trump support, not party affiliation, can be reliably predicted by racial resentment. Support for Rubio is negatively correlated, and support for Kasich and Cruz is not correlated. Secondly, racists primarily supporting Trump does not make them the primary driver of Trump support. You could perform a similar study and find that gays strongly support Democratic candidates; it doesn't mean that Democrats exist because of homosexuality. That kind of polling does little to indicate the proportion of racists in support of a candidate relative to the total base of support. Thirdly, I don't see how they can say race is the primary driving force when they straight-up admit that they control for concerns over economic concerns and etc to isolate the impact of racism alone.
But all of that is what happens when you rely on Salon to perform an honest political study.