It's a basic rule of politics. The fact that you're on their side doesn't mean that they're on your side. Public officials lie, parties change their platforms, politicians cut deals, and journalists are just plain irresponsible. You're asking for grief if you stake more than you can stand to lose on any of them. Just look at the Reform Party.
Life is insecure.
None of us are so powerful that that the game can't turn against us, and most of us could be traded like penny dotcom stocks if we didn' t have a secure stake in something bigger than ourselves. We may not know what deals have been cut in secret, and we sure can't see the future. But we can know the law, and we can tot up the votes. That means we can keep our government answerable to us. Nobody likes to lose an election.