Joe Klein’s source alleges a retaliatory campaign against George H.W. Bush’s adviser and friend for speaking out about the current administration:

It seems a fair indication of the West Wing’s
whigged-out desperation that Libby even attempted the oblique
argument that Wilson was not to be trusted because his wife, a CIA
analyst, had sent him to find out if Niger had sold uranium to Iraq.

But it is an even better indication of how the White House
reflexively dealt with unpleasant news: destroy the messenger. Last
week there was more of the same, according to a prominent Republican,
who told me that the White House had sent out talking points about
how to attack Brent Scowcroft after Bush the Elder’s National
Security Adviser went public with his opposition to the war in the
New Yorker magazine. “I was so disgusted that I deleted the damn
e-mail before I read it,” the Republican said. “But that’s all this
White House has now: the politics of personal destruction.”

Update 11/2: As Andrew points out in comments, National Review’s Ramesh Ponnuru thinks he received the same email, and described it as benign:

I am almost certain I know the email this “prominent Republican” is discussing. It’s too bad neither Klein nor his prominent Republican friend read it. It was not a how-to guide about attacking Scowcroft, and it did not make any personal attacks on Scowcroft. Instead it explained why the author regarded Scowcroft’s specific points and general philosophy as wrong. Is that a terrible thing for the White House to do?

Update 11/8: Via Mickey Kaus, Real Clear Politics has reprinted what it claims is the email sent about Scowcroft. If so, it’s certainly not “the politics of personal destruction.”