Buzzfeed reports that the Romney campaign and the local New Hampshire Republican party organized the gathering to "stand with Cory" at an event in Keene State College, featuring Vice President Joe Biden. From Buzzfeed:
"Vice President Joe Biden needs to face the fact his dishonest attacks on free enterprise have backfired and been discredited by his fellow Democrats," said Romney spokesman Ryan Williams. "And there is no better reminder for the Vice President than seeing Cory Booker's face denouncing his "nauseating" attacks outside his own event."
For context, Buzzfeed provides the following:
Meanwhile, NBC's Carrie Dann reports that 450 people turned out for the Vice President's event.