Well, this morning I voted. I voted in the Kentish Town "Arizona by-election" - caused by the Lib-Dem councillor who thought he could represent an inner London ward from Arizona (he went there to get a Phd.).
Given the unrelenting lies of the Lib-Dems - including the dodgiest of bar charts (not to scale, using the last election but one, putting a text box over the bars to disguise where the zero line was, etc. - all to try and make their real challengers in the ward, the Greens, seem less of a threat) - I was sorely tempted to vote to try and get them out.
In the end, though, Party discipline prevailed, and I spoilt my ballot by writing "World Socialism: SPGB" across my ballot paper.
My way of explaining this strategy, this days, is by likening it to strike action. By consciously applying a political picket line, which says: "We are not going to express priorities and preferences, unless and until this great issue of class is sorted out." They need our votes, our input.
Sometimes it might hurts us a little, as all strike action does, but the final goal is clear.