just for a reality check, i recommend looking in on 538's model. i don't maintain their percentages are extremely precise, but it's good for putting into place the magnitude of how events have impacted the outcome of the race.
for example, before iowa, klobuchar had a less than 1% chance of getting the nomination, and she still does. buttigieg had about a 5% chance of getting the nomination, and he still does. sanders had like a 30%ish chance and it's gone up to 39%. biden was at like 40% and that's now cut in half. and the chance that no one wins the nomination outright has leaped from like 15% or so to 33%.