Many people have strong convictions about politics, and I see nothing wrong with that. Strong convictions are more rational than they are generally given credit for. But they become counter-productive when the politico is no longer willing to listen to outside viewpoints and update their opinions to new information.
This effect can be difficult to gauge in real time, but I have a different question to ask that thrusts at the same point. Ask, "would you prefer that the country receives a negative short run shock in some key indicator, so that your candidate has a better chance of winning?"
Obama supporters might prefer for the economy to continue to fall (even slightly) to boost his chances of winning. McCain supporters might hope for a (small) terrorist attack on a US embassy abroad to boost his chances of winning.
If somebody hopes for a negative short run turn of events for the country just so that their candidate will win, they have gone over the edge. They may argue that over the long run it will be for the benefit of society, but they are fooling themselves. There's no way they can accurately predict future events with that kind of precision; if we can avoid an undeniably negative event now we should do so without hesitation.
Of course, politics isn't about policy.