NEW YORK -- Standing on a drizzly street corner on the Upper East Side, Jack Schlossberg was running out the final days of his congressional primary campaign in a strange tempest of nostalgia and youthful insistence. His television ads have featured the decidedly old-guard Nancy Pelosi, the former House speaker, and his mother, Caroline Kennedy. The supporters stopping to take his picture on the Upper East Side were largely either high school students or retirees.