Bernie Sanders is now the undeniable front-runner for the Democrat presidential nomination, but a long and acrimonious battle between the two wings of the party is set to play out.

Having won New Hampshire, the second state to vote, Mr Sanders has the momentum, and appeared to have consolidated the party's Left wing behind him. But his victory was by a narrower margin than expected, leaving him open to attack.

Many senior Democrat party figures had, until recently, been in a state of denial about Mr Sanders' rise.

They talked about him having a "ceiling" of support, and how the majority would ultimately coalesce around a moderate candidate.

That candidate was supposed to be Joe Biden. But New Hampshire was an unmitigated disaster for the former vice president.