A lot of white Americans are so terrified of being called racist that they feel compelled to support any black candidtate that can even minimally fit a conservative mold. Also keep in mind that most people, regardless of background, have no idea what real conservative thought is and believe people like George Bush and Condoleeza Rice were conservative. The fear of being called racist is so strong that they pass over into the extreme of a soft but real racism of supporting a black candidate regardless of qualification simply to avoid the appearance of racism.
Cruz isn't in the top tier because he's too conservative for the average American. Most Americans are moderate leftists. The younger people, especially, have grown up in a world where denying that a man dressed up like a woman is really a woman is akin to hate speech. People in the younger generations have been so heavily mind controlled that most people in their 20s now believe all the liberal talking points and believe if you oppose them that you're not only wrong, but a bad person too. I had a former friend tell me I was a "terrible person" for opposing gay marriage. They oppose Biblical morality but they have come up with their own replacement moral system. If you talk about the human rights of an unborn baby you are called "ignorant" and "misogynistic", etc.
It's a major uphill battle to try to get through to any of these people. We have to work around their programming somehow.