I don't think there was an intentional plan at first but as Wilson kept running the muck it became obvious that someone needed to get the truth out and this may have been a means of doing so. Libby is the type of person that will go down fighting if the truth can come out and it protects his boss, even if it's just slander like Wilson pulled.
I see that as a possibility. Think about how slimy the Rats are, devising a scheme to smear a sitting president, for which it is illegal to publicize their machinations. I could see someone "taking a bullet" figuratively for the President to stop the Democrat's ploy. Makes my head spin. The Rats operate like the KGB... I guess they were quick learners in that regard.