One thing I heard in the Plunderbund debate chat last night were a few people who have already voted for (or decided to vote for) Jill Stein instead of Barack Obama. This is a terrible decision. Allow me to explain why.

First, I should preface my comments by saying that I’m sympathetic to people who prefer Stein to Obama. In fact, when I go to and take the quiz, the most recent time I have done so it suggested my preferred positions were more in line with Jill Stein’s positions. I still strongly aligned with Barack Obama, but Stein held a slight edge. And I do have specific complaints about Obama’s policies and triangulating, most often that he’s not as far “left” as I would prefer, and believe is necessary for progress.

It would seem perfectly reasonable and rational to vote for the candidate closer to my views. The refrain I have often heard is that “Obama hasn’t earned my vote”. And for a centrist voter, who lies somewhere between the two candidates, this is a perfectly reasonable position. But for someone who finds both of the major candidates to the “right” or “left” of their preferred ideal, it is electoral suicide. At least in a swing state.

There is a theory called the “median voter theorem” that states that the candidate closer to the positions of the median voter wins the election. In general, this is true; and there is a lot of evidence that supports this theory as being explanatory. It also becomes somewhat instructive as an example of how third parties, in our electoral system, act to “spoil” the election and ensure that the winner is the candidate further from the median position (and thus further from the desired position of the people who voted for the “third” party). There is a simplification here that doesn’t always hold – that party positions can be neatly placed on a one-dimensional scale – but an artifact of the way we count votes means we can safely ignore this complication.

Basically, it works like this. We use, generally, what is called “first past the post” voting. What this effectively means is that when a candidate has an insurmountable number of votes, they win the election. In a two-party election, this means having more than half the votes. When a third candidate arrives, it means simply having the most votes, even if it is just 34%. For example, let’s assume that Barack Obama would win a two-party election against Mitt Romney 51-49%. Obama is just slightly closer to the “median voter” position that Romney in this example. Each candidate takes all votes further towards the extremes than their position, and split the voters in between their positions down the middle. Since Obama is narrowly closer to the middle, the size of his voting block is ever so slightly larger. Now let us assume Jill Stein runs, and gets just 3% of the vote. This two percent will be the remote tail further left of Stein; the split of the swing votes doesn’t change. But the election winner does – Romney wins, 49% to 48% to 3%. So, despite being further from the median voter, Romney wins the election. Stein voters get the candidate least favorable. And, perversely, this is unlikely to have the desired effect of moving the Democratic party further left; they can gain more votes by moving closer to the middle, and taking votes away from the GOP candidates.

This video does a nice job explaining how first-past-the-post guarantees that a two-party political system is the only stable outcome of this election method.

We’ve seen this before, with both Ross Perot and  Ralph Nader. But what further complicates the issue is the fact that elections in the US are not determined by a simple vote majority. As we all know, it is determined by the electoral college total, and the electoral college votes are determined on a state-by-state basis. What is the practical effect of this?

Voting for Jill Stein in Nebraska allows that voter to express their displeasure with Democratic Party policies or candidates, but without risking a Romney presidency. Similarly, voting for Gary Johnson in California will not negatively impact Romney’s election chances, if you are partial to the Libertarian Party.

But in Ohio? Well, Ohio’s winner will almost certainly win the Presidency, and the margin appears to be fairly thin. If you are a liberal/progressive/Green in Ohio, unless you want a Romney presidency, you should be voting for Obama. As disappointing as that may be for you, it is the reality of the confluence of first-past-the-post and the Electoral College. Voting for a third party will not suddenly give us a situation where we have three viable choices. If you want more choice in elections, then you need to advocate for a system such as approval voting, IRV, or Schulze method (all of which have their advantages and disadvantages; there is no perfectly flawless answer).

If you are underwhelmed or disappointed with Obama, but prefer a more liberal set of policies, the solution isn’t to vote for Stein. Voting is, quite literally, the least you can do. You need to get out there and be active. Write letters, make phone calls, donate time and treasure to advocacy groups for the issues you care about. Show Democrats what you want, and what you care about. Voting in a way that ensures the guy who doesn’t care about you is in office is no way to promote your policy goals. It is shooting yourself and your issues in the foot.