Dick Cheney seems pretty cocksure about the Rupublican's ability to conduct the war in Iraq, and the Democrats' lack of same, saying of the Dems, "If they are competent to fight this war, then I ought to be singing on American Idol."
Better start warming up those vocal chords. This paper from the APA shows that self-confidence has a very strong negative correlation with actual ability:
People tend to hold overly favorable views of their abilities in many social and intellectual domains. The authors suggest that this overestimation occurs, in part, because people who are unskilled in these domains suffer a dual burden: Not only do these people reach erroneous conclusions and make unfortunate choices, but their incompetence robs them of the metacognitive ability to realize it.