I think that there might be a fundamental challenge in a question like this one because of the fact that Thoreau and Dewey operated in the realm of theoretical and President Obama is a sitting President. In this, the gap between what can be and what should be is accentuated. This is not saying that comparing them is impossible, but rather stresses that doing so compares two different realms. I think that one particular point where the three of them would find agreement is their need to take action in the name of the public good. Dewey's belief on ethical conduct was one that took the subjective and externalized it into the objective, or larger social setting. Consider his words on this point as to how he sees the nature of ethical conduct within human beings:
...the formation, out of the body of original instinctive impulses which compose the natural self, of a voluntary self in which socialized desires and affections are dominant.
This helps to bring out the idea that individual impulses have to be seen in a larger social setting, where compassion and understanding emerge. Certainly, Thoreau would agree with this. His stances on being against slavery as well as war are representative of the idea where "impulses which compose the natural self" are socialized desires." A clear argument can be made that the President's health care initiative is one such example. Regardless of one's political view on the issue, the idea of making it against the law to deny health care to one in need is representative of a subjective "impulse" broadened out in a "socialized desire." The President did not use market restraint or some position of ethical egoism to prevent the bill's passage. At the same time, the President's desire to close Guantanamo Bay and try to redirect it to a point where such a vision is not a part of America's war on terror is another example of taking the subjective desire to breed sensibilities that heighten a great and vibrant democracy on a larger scale. In this, there can be some similarity between the three thinkers on how individuals should act and the construction of society towards this end.