Former US presidents Barack Obama and Bill Clinton have jumped to the aid of incumbent Joe Biden in the election campaign. The three Democrats appeared together at a major fundraising event in New York on Thursday evening. The event at Radio City Music Hall in Manhattan also featured several music stars. Biden’s campaign team said it raised more than $26 million. The campaign show was accompanied by protests against the US government’s Middle East policy, with hecklers interrupting the prominent Democrats on stage several times, and others demonstrating outside. Several thousand people attende…