The 15% rule

In the race to choose a candidate to face Donald Trump in the 2020 election, Democrats allocate their delegates proportionately among those who get 15% or more of the vote in a given state or district. To complicate things, there are delegates allocated at the state level, and delegates allocated by district.

Without getting into the fine details of delegate allocation, I still find this 15% rule a bit strange. It is certainly fairer than to give all the delegates to a unique winner but, as heard in recent discussions, it may have unintentional consequences. I keep asking myself what would happen if seven candidates got each 14% of the votes! I am sure there is a perfectly good answer to this question, but this is not the purpose of this post.

It seems to me that a fairer approach would have been possible, while still implementing some kind of limit beyond which no delegate is awarded. To illustrate this, we will look at the results for the New-Hampshire primary, as published on the NBCNEWS site (with 99% of results in).

Current 15% rule

In the current version of the rule, only votes for the candidates with at least 15% of the total vote counts for delegates. So only 207 700 votes count. The percentage of this value held by each candidate determines their share of delegates. This results in the distribution 9-8-7 (the official result, with all the intricacies of district results and rounding, is 9-9-6). Note that the official list of candidates is longer than the one shown.

Modified 15% rule

It seems to me that that the following rule would result in a fairer distribution, particularly if several candidates share a significant proportion of the votes:

Allocate up to 85% of the total votes to the candidates, starting with the candidate with the most votes, going down. Allocate delegates based on the distribution of votes when this 85% is reached.