You have a valid question but in my opinion you damage your credibility by distorting what is known about Clark. Your valid question in my opinion is why trust a johny-come-lately.
You are skillful with words, I will grant you that. "His record of supporting the worst of the Right- either by vote or in statements..." is a great example. A clue to that "support" can be found in another comment you made: "his history in the military and the mindset it promotes". Sounds to me like you have either an anti-military bias or an outright anti-military position. I heard Clark speak about his personal experience upon returning from the Viet Nam War, of finding that a significant minority of the general public held soldiers in very low regard, and that the overwhelming majority of those who did identified themselves with the Democratic Party. Clark said that, as a youthful officer, he did not feel welcome in the Democratic Party. Many of his fellow officers had the same experience. Despite that personal villification, Clark remained an Independent. I care much more about Clark having voted Democratic in the last three Presidential elections than I do about him having voted for Reagan.
I also worry a lot more about who is on the long lists of corporate donars to prior election campaigns of some of our other Candidates than I do about Clark's brief "corporate alliances" as you call them. Regarding many of the debunked accusations against Clark that you cite, may I suggest that you and any other open minded Democrats please visit
http://www.ex-deaniacsforclark.com/ where thoughtful non inflamitory arguments are presented, in depth, regarding all of those "concerns". It, by the way, is in no way an anti-Dean site, the people who have launched it still hold Dean in high regard, they just prefer Clark and explain why.
The thing is, it is my opinion (warning subjective commentary alert) that the Republican operatives have already thrown the kitchen sink at Clark, and he is still standing. You know the line in "I shot the Sheriff", which I think goes "he said kill it before it grows"? That has been the Republican strategy regarding Clark.
Rightly or wrongly (and I conceed they might be wrong) the Republicans did not adapt that strategy regarding the current Democratic front runner, Dean. They may well have underestimated him, but the juicy stuff against Dean is starting to be rolled out right about now. Aside from a few Democrats nipping at the edges, there is a host of unexploited contradictions between the "Old Dean" positions, actions, and alliances he had back in his days as a Clinton Democrat Gov, as contrasted with his current stands and backers as the progressive insurgent movement Presidential candidate. Dean has taken a lot of corporate money while running for prior office, and he mostly governed from the center. There is a lot of "flip flop" ammunition that can be used against Dean by the Republicans.
With Clark, one has to decide whether you believe he is inherently who he says he is, or an imposter. Some might believe the latter, but I don't, and I have paid very close attention to Clark because I personally am a life long leftist who cares a great deal about whether my candidate is posing as something he isn't. There are many others like me who approached Clark with some suspician, studied him closely, and now are grateful that our Party has someone of his bredth, ability, and yes, caliber, to carry our banner in the coming election.