It will be interesting to see how a multi-candidate Democratic field plays out with their proportional system. Will the 15% threshold and fear of a chaotic brokered convention make for a Duverger's Law on steroids, or might we actually see multiple strong candidates after the first few contests?
I can't see anyone tactically voting in the early primaries just to avoid a brokered convention. People will tend to vote candidates who they think have a shot at the nomination, sure, but IA, NH, etc. is way too early for any kind of "we have to prevent a brokered convention" argument to take hold.
Obviously IA, NH, SC, etc. are too early for this dynamic to take place, but consider what happens if the 2020 Democratic primaries play out similarly to the 2008/2012/2016 Republican primaries. A field whittled down to 3-4 viable candidates worked out for the GOP since eventually they ran into primaries with winner-take-all and winner-take-most rules, but it would not necessarily work out for the Democrats under their proportional rules. Will the superdelegates simply coalesce behind the frontrunner en masse come late April to avoid a brokered convention, even if it looks like he/she may only end up with ~40% of pledged delegates?
