National primary turnout (as a whole or for any one party) is neither really meaningfully comparable across elections (because of changes in methodology of particular primaries, changes in timing between primaries, differences in the course of elections which change the perceived value of voting in later primaries, etc.) nor predictive of general election turnout (so pointing to primary turnout as evidence of a party's or its nominee's strength in the general election is meaningless.)

Oops, you are right! I misread that graph. I'm sorry - you are absolutely right. My eye followed those curves backwards and mixed them up.

Thanks for a polite correction :)