Remember the true currency of politics is votes not money. As long as its one person one vote the 99% actually have the power, they just fail to use it. Party loyalty is one of various examples of how the 99% fails itself.
The 99% always have the power. No dictator can rule without the approval - however grudgingly given - of his subjects. So why do they give that approval to someone like Saddam? Because in their mind there is an internalized image of the nation they happen to identify with, which is constantly telling them how to act, speak and think, and which gets constantly reinforced by and synchronized to other people's actions and reactions.
So why do people vote against their own interests? Because they're a member of a Group (democrats, republicans, evangelicals, greens, communists, whatever), and members of a Group vote in a certain way. Or, put another way, a person is a part of a community but the community is also a part of a person. So people are actually voting according to their interests, just not their personal interests.
I suspect the next big leap in human evolution is becoming fully aware of this mechanism and bringing it under conscious control. Currently it isn't, which is why strong identification with a group - such as a particular nation, ideology or religion - tends to lead to highly irrational behavior. Such groups don't have brains of their own, after all, so if the members just blindly obey, the end result is that it can't evaluate its own actions. We need more patriots who are willing to criticize their nation/church/party/shady backroom club/whatever, to treat it as a sports team that needs to be whipped into shape rather than an idol to be worshipped.