https://www.nytimes.com/2020/03/01/us/15-percent-rule-democratic-delegates.html

This article outlines a new rule for the Democratic Party that requires candidates to receive 15% of the vote in congressional districts and state-wide districts in order to be considered by delegates. Further, those who receive at least 15% of the vote receive a proportional amount of the delegates in those state primaries. The main concern for this model is that the nomination process will take much longer.