The why is pretty obvious, she doesn't want her life turned into a cartoon characterization of a bimboo, as has happened to just about every women that has dissed a democrat. Women that out democrats are distroyed by the press and the public. This one appears to smart to fall into the trap.
You guys write this down - This story has Clinton written all over it. Hillary got scared that Kerry was going to win and pushed this out. That would cut her out until at least 2012 when she is likely to be too old and either out of the spot light too long because she gets beat in '06 or with too much of a voting record in the Senate to be a contender if she wins reelection in '06.
As someone else has said on an earlier thread, it is unlikely that Bush pushed this out since he has a better shot against Kerry than Edwards and it would sting all the Democrats more to have this out about the time of the Democratic Convention when Kerry has won.
Hillary's plan is to either get drafted at the Dem Convention because no one can get a majority, or to run in '08.
There will be a lot of folks looking for Rove's fingerprints on this story, but they will not find them there.