Should Progressives Feel Obligated to Vote for the Democratic Party?

Daniel Davies at the Crooked Timber site sayeth thee nay. Some of his reasons, which also amount to a pretty good case (one I've made before) for not voting at all on candidate elections:

Not only is it highly unlikely, for paradox-of-voting reasons, that yours will be the crucial vote, but even if it is, it will have elected a candidate who is then highly unlikely to be the crucial vote on any proposal of interest, and who cannot even be relied upon to vote the right way if he is. So given the generally lower level of stakes, an election like this one is likely to be a happy hunting ground for protest votes. And so this is a serious business – I really do think that more likely than not, most CT readers with a vote to waste should be giving serious consideration to wasting it….

…the problem to overcome in getting you to drag your ass (note American spelling) down to the polling station is the Paradox of Voting. Which isn't really a paradox; it could more accurately be titled "The Actual Extremely Low Expected Value Of Voting". This requires an appeal to your civic sense of duty; remember Martin Luther King, etc. In other words, they need you to see it as your duty to society to vote, or alternatively to see your vote as an important form of political expression.

However, once your ass is duly dragged and you're in the voting booth, the last thing they want you to do is your civic duty (which would be to vote for the candidate you think is the best; that's how voting systems work, strategic or tactical behaviour is a pathology of a badly designed system) or political expression (which also wouldn't have you voting for their guy). Once you're there, they want to argue in purely instrumental terms – you have to vote for the Democrats because if you vote for your minority party, you have no chance at all of being the marginal voter.

It looks inconsistent, because it is. Particularly in a midterm election, when you have a very small chance of being the deciding vote for a Congressman who in turn has a very small chance of being the deciding vote on an issue of importance (and given that this is the Democrats we are talking about, you have to take into account votes of importance where your congressman is the swing vote for the wrong side), the expected value of your vote is very small indeed, and the costs of it are the psychological toll on your own morale, plus the opportunity cost of whatever else you might have done with the time.