I'd like to hear responses to the following simple argument that voting for Nader in 2000 was at least as rationally defensible as was voting for Gore.
Either (a) a choice of vote should be based only on the expected value of its impact on the outcome of the election, or (b) it should be based on other considerations, such as, to name a couple of possibilities, the value of expressing one’s political opinions, the value of avoiding pangs of guilt, a civic duty to vote, etc. If (a), then the choice of whether one should vote should also be based only on the expected value of the impact on the outcome of the election and, therefore, leftists (nor anyone else for that matter) should not have voted, and everyone who did vote was equally irrational in doing so, given the vanishingly small probability of casting a vote that would have changed the outcome of the election and the small but genuine costs of voting. If (b), then it was rational for leftists to vote for Nader if they had the appropriate expressive preferences or if a civic duty required sincere voting of them, etc. These conditions were met for most Nader voters if they were met for most Gore voters. Hence, (most) Nader voters' vote for Nader was just as rationally defensible as the choices of (most) Gore voters.