If the Wilson/Plame affair ends up having a longer, and ultimately more damaging, half-life than any of the other Bush administration mini-scandals (Enron, Halliburton, the Cheney Energy advisors, the original uranium flap), I suspect one key reason might lie not in the content of the scandal, but rather the form. Unlike those other controversies, Wilson/Plame has one key ingredient to its story: a Deep Throat.
There is irresistible, itch-you-can't-stop-scratching quality to a Deep Throat narrative. Whenever someone comes up with a new speculation about the original one, it generates a week's worth of coverage -- and that story is thirty years old! The press will keep clawing away at this new version, until the leaker is revealed (it helps that the leak itself was a criminal act, of course.) It gives the whole story a far more coherent arc -- it makes it a literal whodunit, as a opposed to a "did the White House know that there was some suspect intelligence information in the State of the Union?"
So if there are any structuralist literary critics on the White House payroll, I'd imagine they're advising the President to get out in front of this one: if they know the leaker's identity, they should hand him/her over to Justice immediately. Otherwise it's just going to fester, and maybe explode.