I am pretty sure I read that, in general, 90+% of registered Ds vote D. Same thing for Rs voting R.
For the record, I’ve been a registered Democrat since 1988 (my first presidential election). I was Operation Chaos 20 years before Rush coined the term.
I love messing with their primaries.
My parents did that in the 60’s and 70’s. Registered (D) so they could vote for the weakest candidates in the primaries........