This is the end of the Bush presidency. All the ingredients are here. Bush immediately addressed the nation. Why? He knows how big this is. Almost no one likes Bush, but it appears that he has been spying on everyone. The people who are angry about this will be a much more angry and vocal group than the people who are willing to apologize for it.
It is simply not possible for someone this unpopular to violate everyone's privacy and get away with it. Investigating the phone companies is the key. Spector is already calling for it. The phone companies will be the dominos that lead to Bush's impeachment. The Republicans cannot defend the phone companies, and once the phone companies are investigated, there is no stopping this train.
The important thing is for all of us to recognize that this is the Big One. This ends Bush's presidency. Game Over. When the scale of this gets out, even Republicans will support impeachment.