Outside, the gathering verged on a street brawl. The opposing forces lined up like screaming armies on either side of the street, about 1,000 people a side. Diane Campbell of Kingston, N.H., held a sign with Mr. Obama's face superimposed on a Nazi storm trooper, a sign, she said, that was made by her chronically ill mother. Her mother's hereditary autoimmune disease is treated with expensive transfusions of gamma globulin, paid for by Medicare.