He gets support from people who don’t like Trump but don’t want another Bush.
And, as others have noted, they tend to be people who aren’t real interested in policy or political “inside baseball”, they don’t like politicians, they just want someone they think they can trust.
In other words, the kind of people who Trump attracts, but who don’t like Trump, go for Carson. Even so, I suspect that most of Carson’s supporters will go to Trump if he bows out.
I think that's wrong, unless you're speaking generally. Trump leads with every demographic, very conservative, not so conservative, moderates, liberals, the young, African Americans and Hispanics-- except the elderly and very religious segment.
This is the Church Lady vote.