Did Nixon order the Watergate break-in?
What many people forget is that it has never been proven that Nixon knew of or approved of the actual break-in of the Democratic headquarters that ultimately resulted in the scandal that brought down his presidency.
Yes, a lot of other malfeasance was proven, but the criminal offense that started it off was never directly linked to Nixon.
Lesson: it is not necessary to link the outing of Valerie Plame to Bush in order for him to be permanently crippled by the revelations from this scandal.
Did Nixon order the Watergate break-in? We will probably never know. But we do know that he ordered the coverup.
Did Bush authorize the outing of Valerie Plame? We may never know. But we do know that he authorized the release of national security secrets for the purpose of protecting his political butt.
It is not everything. But it just may be enough.