I think your description is how it is supposed to work, and Designer's is how it actually happens, because of a lack of understanding and participation on the part of the American people.
OK, I'll accept that explanation. But I still think that no candidate would reach the level of major party nominee if the majority of average Repub voters were strongly opposed to him or her being in that position. I don't remember any nominee of the convention who was rejected by a majority of voters in the primaries.