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Cox: Electoral rules and electoral coordination

Disclaimer. Don't rely on these old notes in lieu of reading the literature, but they can jog your memory. As a grad student long ago, my peers and I collaborated to write and exchange summaries of political science research. I posted them to a wiki-style website. "Wikisum" is now dead but archived here. I cannot vouch for these notes' accuracy, nor can I say who wrote them.

Cox. 1999. Electoral rules and electoral coordination. ARPS (2):145-61.

In Brief

Electoral coordination occurs at two levels: (a) at the district level and (b) at the national level. We know quite a bit about (a) (see Cox 1997), but far less about (b). (There is also a third level: coordination to distribute porfolios (in the cabinet or committee chairmanships), but Cox decides not to discuss that.)


These are all based on ENPP:

To measure linkage (b), use an inflation factor to measure how much higher ENPnat is than ENPavg. If I = 10, then about 10% of the size of ENPnat can be attributed to poor linkage (i.e. localized parties). Perfect linkage would have I = 0:

(a) THE DISTRICT LEVEL: Two distinct M+1 rules.


This is where most of the action is: Parties, factions, and groups must decide who will run candidates--and how many each faction will run. They will coordinate in a Duvergerian manner (using Cox's M+1 rule) when three conditions hold (illustrated in a first-past-the-post district, but true elsewhere):

  1. Everyone agrees that only two (M+1) parties have a realistic chance of winning. If we think that an extra party has a good chance, then there will be too many candidates.
  2. Everyone agrees about which parties have the most realistic chances of winning.
  3. We have short-term, instrumental preferences. If one party is trying to develop itself over the long term, it might run even if it knows it can't win right now.


If parties don't regulate entry (i.e. they overnominate), then voters are likely to channel their votes primarily to the top candidates using the M+1 rule. Assumes that voters are instrumental and interested in short-term victories.


Use "I" (inflation factor--see above) to measure degree of each state's linkage. Linkage (Y) varies in response to two variables:

Evidence for X1 and X2:

Research by the same authors

Research on similar subjects


Cox, Gary W. (author)Comparative PoliticsElectionsElectoral RulesCoordinationPartiesParty SystemsLinkage

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