re: "I'd rather have an incompetent clown as my opponent than someone who might actually be able to accomplish something"
Do you want your party to succeed? Or your country?
On most subjects we disagree with a class act like Joe Lieberman. But we prefer him as an opponent to the McKinney types. That is because Lieberman truly wants what is best for the country. He pulls us up to his level of debate. McKinney pulls us down to her level of debate.
Lieberman is an exception and his party gave him the boot because of it. 90% of politically active Democrats are actively working to bring this country down. They are the enemy of both our party AND our country and so long as we have to confront them politically I'd rather they be as incompetent as possible.