Update: Patterico has video of Obama denying the mandate is a tax. This is a great day for politicians who want to have their "I didn't raise taxes" cake, and eat it too. Obama can pretend he didn't raise taxes because it is not called a tax, but gets to keep Obamacare as a law on the taxing power.
Update (III): Jim Geraghty outlines what it takes to undo this. I see that Romney can to much by himself, and even more with a majority in Congress, but can he get rid of all of it without a filibuster? Its unclear.