I actually do agree that withholding a vote CAN be a powerful political statement.
In this election, we have potential vote withholding strategies on both sides.
On the Republican side, we have Evangelicals who might be upset about McCain's moderate past. I view this as highly unlikely. And Bob Barr also acts as a safety valve voting option within the system.
On the Democratic side, we have white, working-class voters and, to a lesser extent, older female Hillary Clinton voters. I think that most of these will eventually vote for Obama.
However, Obama was never a good pick if the goal was to attract the white, working class. This was made abundantly clear in the primaries. And, in fact, the push for an anybody-but-Hillary candidate was a power-play on the part of Democratic liberals to gain party supremacy from the moderates. And, in fact, the Obama candidacy has always been a reckless endeavor. The clearest path to victory this year was always party unity behind Clinton. By choosing Obama, they placed victory over another party faction ahead of victory over Republicans.
So, let's say that a Democratic Party moderate wants to send a clear message that moderate issues need to be heard in the party. Voting for Obama will never get that message across. Voting for McCain is selling out. Staying home is a legitimate strategy to send that message.
Note: I DO NOT recommend this strategy. Obama is, for me, a bitter pill to swallow. But I will vote for him and the Democratic moderate Mark Schauer and Democrat pro-lifer Dudley Spade and hope that these moderate Democrats will uphold the moderate view within the party.