Barack Obama

Scenario One: President Obama proposes an ACA that, per his earlier promise, includes a robust public option.
Scenario Two: President Obama proposes the ACA as he actually proposed it, and Sanders offers an amendment to add a robust public option.

In your view, these two scenarios are fundamentally equivalent in terms of what might actually get passed. Therefore, faulting Obama for not doing the first requires one to fault Sanders for not doing the second.

For my part, I see those two scenarios as being very fundamentally different. What the President of the United States says and does has a huge impact on the political landscape. Whether a particular policy change can be passed is not a given, pre-existing fact; it's affected (not totally controlled but powerfully affected) by the President's choices. It's affected by an individual Senator's choices, too, but to a far lesser extent.

If Obama had proposed a health-insurance reform bill that included a public option, and then found the public option eliminated by a coalition of Republicans and conservative Democrats, there would have been much less basis to criticize him. At least he would have tried. He might have succeeded, by playing heavily on party loyalty. Even if he failed, taking a more progressive position would have helped to shape the public discourse. Those of us who criticize him from the left would be much less critical on this particular issue if he had handled it that way, even if the ACA as actually enacted had turned out to be exactly the same. In contrast, there was nothing Sanders could do that offered the slightest possibility of adding a public option, once Obama had proposed an ACA that excluded it.

I just picked the ACA as one example. There are plenty of others, notably appointments (Geithner and many other examples), where Obama made the effective choice and a progressive Senator, confronted with that reality, had no available course of action that would put a better person into the office.

Obviously there are cases (such as closing Guantanamo) where not even Obama's political power is sufficient to achieve a good result. There was a time when I was critical of Obama over Guantanamo, but when I learned more about the issue, I changed my mind. One could find some details where he might have done better. Overall, however, the blame on that issue lies with Congress. I don't blame Obama for his failure there because at least he tried. That illustrates my point that each political actor's conduct should be assessed according to the options that were open to him or her, given how other actors are deciding. It's not a double standard to judge different officials differently when the practicalities of the situation are that they had different options open to them.