I'm confused by the math used for Iowa caucuses. Here's an example:

enter image description here

So there were 70 attendees. A total of 8 delegates assigned to the caucus

But after taking into account viability... 9 votes were not viable and I assume those people just left...

But the delegates are still being apportioned out of 70 instead out of a total of 61 (seems strange to me)... So this leads to 2.057,1.7,3.2... if all rounded down we get 2,1,3... a total of 7 delegates. Finally it seems like to correct this to get 8 total... the delegate with 3.2 is rounded up to 4.

Is this really how this is supposed to be done? Is there some site where the specific instructions are given?

  • 4
    I like how for Sen. Warren they put Warren but for Sen. Klobuchar (Klobushar? Klobasher?) and Mayor Buttigieg (Buttigeig? Buttagig? How do you say that again?) they just put Amy and Pete.
    – Damila
    Commented Feb 6, 2020 at 3:03
  • @Damila It's called "being folksy" apparently...
    – corsiKa
    Commented Feb 6, 2020 at 17:18

2 Answers 2


According to a training presentation from 2016 (slide 40), when computing viability all fractions are [to be] rounded UP to the next whole number.

enter image description here

Also (slide 47) the viability threshold is not recalculated if some attendees leave; only the initial attendance figure when proceedings opened is used throughout.

enter image description here

The fractions used to award delegates are normally rounded up or down at the 0.5 threshold (slide 51)...

enter image description here

... but if not all delegates could be allocated this way, then the leftover is awarded to the group with highest decimal below 0.5 (slide 56).

enter image description here

So the calculations from the image you've posted are actually correct according to these rules. The last fraction 3.2 was rounded to 4 because 0.2 is also the highest figure below 0.5 in that column: the first figure has 0.05 (so less than 0.2), while the 2nd figure has 0.7 (which is above 0.5) so it is discarded...

They even show an example (similar to the one you posted) on their next slide:

enter image description here

Note that you can also end up with too many delegates by the initial rounding process. In that case (slide 58) a delegate is subtracted from the group with the lowest decimal above 0.5... as long as it's not a group with a single delegate, i.e. those are excluded from this latter elimination process.

enter image description here

Also (slide 60) if there's a tie as to whom should lose a delegate (between two or more groups), it's decided by a coin toss or drawing names from a hat.


Yes, that's roughly how caucusing works.

I've done it at state and county party conventions before. The whole body gets a representation based the size of the body (or some other set critera), and then breaks up into groups by interest. There's a "viability" threshold set at a certain number of members, and if some of those groups aren't viable, they have to join groups that are. Each group then gets to choose a certain number of members to represent that caucus group at the next higher level (eventually leading to being actual delegates at the DNC or RNC). Those folks you'll see this summer at the DNC in the funny hats next to the sign reading "Iowa" will have been selected from these caucus groups.

If someone doesn't want to join any of those other groups, or has to leave mid-process for some other reason, that doesn't change how many delegates the entire body gets. However, it of course does alter the relative representation of any group they might have joined, but didn't.

It this particular case, it appears that Sanders partisans in particular were rather apt to fail to join any other group if theirs happened to not be viable in their precinct. I saw at least one instance of that happening with Yang and Buttigieg supporters as well though.

  • 1
    Thanks... but is it correct to keep the total at 70? If you look at lines A,B,C... the total attendees left is 61... but it is apportioned according to a total of 70 in the 4th column (which I assume is the pre-realignment total). This is the part that confuses me. Commented Feb 5, 2020 at 12:46
  • 1
    @AmeetSharma - Most likely is it, yes. Notice those slots that 70 is in are all labelled "Eligible Caucus Attendees". That smacks of a specific term of art listed in some bylaws somewhere (which I suppose someone with access to Iowa Democratic Party bylaws could probably go dig up), but the wording implies that just attending is sufficient. In general you don't reduce the entire body's representation numbers just because some people left in the middle or choose to abstain.
    – T.E.D.
    Commented Feb 5, 2020 at 12:52
  • Thanks. It seems strange to me because adding the total delegates without rounding is 6.97 (which is (61/70)*8). Then the rounding is fudged afterwards to make the total 8. Commented Feb 5, 2020 at 13:04

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