I live in a Tory constituency where Labour has no chance at all. I pondered a tactical vote on the basis that I have been proposing - if in doubt vote against. In the end however I voted as I have done in every election bar one (and that was tactical) to support Labour. I did so because at heart I still believe the principles it espouses are the right ones. I did so because no other party is likely in the end to really empower those people who don't have it now. I did so because no other party with a realistic chance is likely to make a real effort to deal with climate change. I did so because no other party is likely to make the effort needed to adress the problems of Third World debt.
So - if you haven't voted yet do so - and do so for the only party likely to make a real difference.