Scott Adams envisions one:
Imagine a democratic political system in which no one is allowed to be a member of a political party. How would things be different? My hypothesis is that confirmation bias, or cognitive dissonance, or something of that nature, influences voters to irrationally agree with the platform of their own party no matter what the facts suggest. My hypothesis is easy enough to test. All you'd need to do is come up with a phony issue and present it to your test subjects as something to which their party agrees, or disagrees, and see if party affiliation influences opinions. I think the effect would be large.