"A big effing deal" is how one pundit put it, borrowing one of Joe Biden's most famous lines. Barack Obama's former vice-president has won the lion's share of Super Tuesday primaries and leap-frogged Bernie Sanders as the frontrunner to win the Democratic nomination for US president. The race is far from over, with nearly two-thirds of delegates still up for grabs. Have moderates coalesced for good around Biden and does he have the right stuff to take on Donald Trump in the fall?