Fun Friday Primary Math

Ben Tulchin is one of my favorite people.  So I agreed with him wholeheartedly when he pointed out the new top two primary system, "is exponentially more complicated than a traditional primary system."  Probably the biggest complication of the top two primary system is figuring out what districts are likely to product top two contests between members of the same party.  This has a huge impact on strategy.  In a safe district do you hold something back for November?  Or do you go all in next month hoping to face a patsy in the fall?  Answering that question is, well, complicated.

Actually, the first couple of parts of the answer are pretty simple.  Despite their growing registration Independents simply don't play in primaries, at least not yet.  Not enough turn out.  And those that do tend to split their votes between the major parties in roughly equal portions to the make-up of the major parties in the district.  In other words, they are a wash. 

Further, registered members of the major parties tend to vote for members of their own party.  Dems vote for Dems.  Reps vote for Reps.  Even if it might be more strategic for them to vote for the "best" candidate of the other party they just don't.  So once you make educated assumptions about what percentage of the electorate you think each party is going to make up you can make some pretty good assumptions about what percentage of the vote candidates are going to be fighting over.

And that is where it gets complicated.  Take a district where Democrats are going to get about 70% of the vote and there are two Dems and one Rep running.  If you assume that the Dems each get about half of their vote they each will get about 35% of the overall vote and finish ahead of the lone Rep with 30%.  Viola.  Dem on Dem violence in the fall.  Special interests have something to spend their money on.  The press has something to write about.  Everyone is happy.

But candidates don't divide up their party's pie equally (and yes, I know the point of the top two is to get people to stop thinking in terms of partisan pies... but until voters stop acting that way, I'm not going to).  In 2012 there were 123 situations where two or more members of the same party ran in the same district.  The top vote getter of a party averaged 63.4% of the votes cast for members of their party.  Second place on average was worth only 28.3%. 

So what is the takeaway?  If you are looking for same party top twos there are three places to go.  Start with the easy ones where there are no candidates from one of the major parties.  Those made up half of the same party top twos in 2012. 

If there is only one sacrificial lamb the district had better overwhelmingly tilt towards one party.  Those contests produced a quarter of same party top twos.  In those cases the party that got blocked out of November got 25% or less of the partisan primary vote in every case but one. 

Finally look for the places where chaos has broken out and there are two or more Democrats running and two or more Republicans running.  Those made up the remaining quarter of the top two contests in 2012 and are probably the contests keeping folks like Ben up at night.