Abdi says reaching Iran-P5+1 accord mostly matter of domestic politics; both side's negotiators face internal critics; in US, AIPAC pressures Congress, in Iran, those fearing no end of sanctions despite concessions; as Republican hawks take power in January, promising new sanctions, talks face new challenges requiring mass organizing to protect them; will be issue in president race as Hillary runs to Obama's right. Abdi not optimistic but recalls success of public opposition to bombing Syria.