Why are Pundits on the Left More Willing to Criticize Their Own Team?

Why is the left so much more willing than the right to criticize members of its own team when they mis-step? There seems to be far more people on the left criticizing Obama than Republicans criticizing Bush, especially when it comes to economic policy. Why?

A.  There really isn't a difference, both sides are equally willing to criticize their own team. Look at how the left backed off on the war once Obama was in charge.
B.  The Obama administration has made more and bigger mistakes.
C.  Republican pundits face a much larger penalty when they deviate from the team message, criticize policy, etc.
D.  Democrats are a much more diverse group, including and perhaps especially when it comes to economic policy, so disagreements are more likely. There is no single, dominant, well-known party line on every issue as there is for the GOP.
E.  It arises from a fundamental difference the psychological make-up of the two sides, with the right far more likely to be populated by leader-follower types than the left. Sheep can be herded, cats cannot.
F.  The left has been losing ground the last few decades as market fundamentalism, attacks on social programs such as welfare, and so on have taken hold, and hence there is considerale frustration with Obama's inability to reverse those trends.
G.  The media is more likely to highlight disagreements on the left.
H.  The left is more likely than the right to sway leaders toward the policies they favor, so they are more likely to speak ou when they disagree
I.  Other

I think there is a diffeence, so A is out and I don't think it's because there were more/bigger mistakes by Obama, especially if we expand beyond economics to the war. So I won't choose B either (I've been disappointed with the left on its willingness to criticize Obama on the war/civil liberties issue, but I still think there's been more opposition to Obama from the left than there was for Bush from the right, but that may be because there was more agreement with the policy on the right). Answers E, F, G, and H don't ring true, at least to me, so I think it's mostly a combination of C and D. But I also have the feeling I'm missing something. What is your explanation, if you think one is needed? Is it on the list? What should be listed under "other"?