2 possible things could happen
FIRST: He survives this week, and they realise he's the sole threat of being the winner, so decide to keep nomming him in order to increase his chances of being evicted, and therefore eliminating the sole threat.
SECON
He survives this week, they realise the public like him and so forge allegiances with him in an attempt to gain Halfwit's fanbase and potentially overtake him.