If the Left's tendency to punish these imperfect Democrats for their transgressions had led to some positive result, then the argument could be made that more than vanity was involved here, that the effect of causing some Democrats to lose was to make later Democrats more progressive and thus more favorable to the Left. Or maybe that the Left is on its way to building a viable third party that can win nationally.
But any examination of those three case studies -- Elections 1968, 1980 and 2000 -- would lead to a conclusion that whatever practical goals that some on the Left had in mind were not advanced by the Democratic defeat. The Democrats did not become more progressive, rather they shifted more to the center.
All three Republican presidents -- Nixon, Reagan and Bush-43 -- extended or started wars that their Democratic rivals might have ended or avoided. Those elections -- plus congressional outcomes in 1980, 1994 and 2010 -- also bolstered the Right and helped consolidate anti-progressive attitudes on domestic and foreign policies.
More than four decades after 1968 and a dozen years after 2000, there is still no left-wing third party that can do more than play the role of spoiler.
Yet, if there has been no positive practical result from these electoral tactics in the past -- and there is no reasonable expectation for the future -- then what's the point of repeating them? There's the old saying that one definition of madness is to do the same thing over and over, expecting a different result.
Nor, by the way, is there a popular movement that can significantly alter government policies strictly through civil disobedience or via protests in the streets -- with all due respect to Occupy Wall Street. So, what's up here?
The only explanation that I can come up with for throwing away a vote on a third-party candidate or not voting for "the lesser evil" is that such a choice represents a personal expression of anger or disappointment. And I don't mean to disparage anyone's right to feel those emotions. Given the recent history, it's hard not to.
But -- when some lives can be saved, when some wars can be averted and when the planet can possibly be spared from ecological destruction -- the true moral imperative, in my view, is to engage in the imperfect process of voting for the major-party candidate who seems more likely than the other one to do those things.
To ignore that imperative, I'm sorry to say, is an act of vanity.