At this point, Clark is breathing but must change the dynamic of this race.
My suggestion - Project how each of the other candidates who have won primaries will be attacked by Rove in the Fall. And how those attacks will not work against Clark.
Everyone knows what they are, except the Dem electorate. Clark has to do this now.
If he is running to be President that is. Edwards seems content to accept the VP slot, more power to him. Clark should demonstrate that he wants the top spot by going after Kerry and Edwards on electability.
It may not work, but it's the best chance in my view.