Due to the major demographic changes we have gone through in the last few years in this country, we will be a majority/minority nation and there are a large number of people who do not like that. Donald Trump has tapped into those people's fears because he comes from the extreme right wing part of the Republican Party, as does Ted Cruz. They believe that we should cut taxes to wealthy Americans and enforce anti immigrant laws. They don't believe in Education or Social Security, they would end it and change it and privatize it.
