Useful guidance

For those who haven't yet seen Alice's post on the dangers of strategic voting, it's definitely worth a look. While I've discussed before the benefits of voting for the party one most agrees with rather than some lesser choice, Alice's post is particularly important in recognizing the types of incentives created when a party is able to successfully convince voters to vote "strategically" as the term is usually understood:

I am sorry to say this, but people who claim to be "voting for the environment" are spending more time poring over past voting statistics (as prepackaged and interpreted for them by others) and daily rolling-polls, than they are actually spending poring over the environmental platforms and proposals of the political parties they are considering voting for. In the Skinnerian world of electoral mandates, these voters are unfortunately and unwittingly rewarding cynically manipulative electoral strategies, rather than thoughtful platform development, in our politicians. And afterwards they'll be more disappointed than ever...

If all a politician has to do to get your vote is convince you they're more likely to win, just think what kind of Parliament you're going to get: an even scrappier place filled with people who've learned the only way to survive is to win at all costs.