the worst foreign policy blunder in the modern history of america? and let me give you a hint. it wasn't bernie sanders, it was hillary clinton. >> clinton's speech today overshadowed sanders' big address, defending democratic socialism. hundreds of students lined up in the rain at georgetown to declare there's already socialism, for the 1%. brett? >> ed henry in new york. isis and the refugee issue are permeating the republican race. chief political correspondent carl cameron shows us how a make foreign policy issue is playing among some of the nonpoliticians in the field. >> in alabama, ben carson defended his assertion that isis is a bigger threat to the u.s. now than al qaeda was in 2003 when the iraq war began. added that isis is a bigger threat than al qaeda was even on september 11th, 2001. >> you didn't have to be all that great. you had to be able to fly some planes. and get a couple of people in