As ThinkProgress understated it, it's just "another sign that the Romney campaign doesn’t appear to speak for its candidate."
In the reassuring afterglow of a Romney campaign spokeman's unambiguous declaration that the "mandate was not a tax," which was contemporaneous with a Romney campaign spokeswoman's unambiguous declaration that "Governor Romney thinks [the mandate] is an unconstitutional penalty," Governor Romney now unambiguously declares that the mandate "is a tax" (although his mandate was not).
Don't ask. It makes as much or as little sense as you want it to. It's auditor's choice. In RomneyWorld it's a tax or a penalty or the Easter Bunny--and what it is in your world depends entirely on which "reality" you choose to accept. Should you be a citizen of RomneyWorld, however, you are unbound by facts, unobligated to history. You are free, free to accept and defend any shifting explanations or shifty flip-flops you like.
For comfort, look at it this way. Romney's position(s) on the mandate is at least as conceptually solid as Joe Stalin's 'Popular Front.' The mid-1930s communist international movement was designed to oppose German fascists, until Joe, in 1939, signed a treacherous deal with the German fascists, at which point the movement was expected to love German fascists. Two years later, the fascists returned the treachery and everyone standing with Joe was expected to hate the fascists again.
Whatever it takes. Whatever it takes.
That is Mitt Romney's only reality.