The first type of Democrat is the type that would vote Republican now if they reevaluated their values and how well the Democratic party platform matches them.
For instance, I worked with a lady who was a rabid Democrat and voted for no other party ever. She was against gun control, carried a pistol for self defense, was very religious, was adamantly opposed to abortion, and detested gay people, welfare, and taxes. The only thing the Democratic party stood for that she stood for was labor unions.
OTOH, my dad was a union worker (same union as this lady in fact) and he voted Republican because he knew that the Democratic party stood for nearly everything he was against.
The biggest difference between him and her was that Dad paid attention to what he was voting for and she didn't.