The campaign is over.
Not that I am defending Sanders, I think he is a hypocrite.
As a generic Senator you are an equal member of government as with the executive and the SCOTUS. They are under no obligation, other than manners, to be seen marching up the street.
The voters in the US still operate under the delusion that the President is the decider—he’s not supposed to do a damned thing that Congress doesn’t tell him to do. We really need to go back to Congress being involved with what we do, and where we declare war.