Me three. I believe in Michigan (and perhaps other states) you could vote in the primary (at 17) if you would be 18 by the time of the general election. I may be misremembering of course, but I do remember that Jesse did particularly well in Michigan, winning the caucus! Now what I am having trouble tracking down is whether Michigan had a primary and a caucus even back in 1988, but I think it must have, as I voted for Jackson at a poll location and it wasn't anything like the crowded rooms of a caucus. I wouldn't have any idea how to participate in a caucus back then and certainly wouldn't have had the time. (Or maybe it was enacted just like a standard primary but they called it a caucus? That might be the most likely...)
Years later, I actually saw him and David Dinkins and Mario Cuomo at a big march on Washington (Save Our Cities march, probably in 1993).
RIP.