While this (Decima) poll is not too bad, this one (Angus Reid) is downright ugly.
I am reminded of of the Ali-Foreman fight:
Ali instead started to lie on the ropes towards the end of the 1st round, and used the ropes throughout the rest of the fight. Foreman's strategy for the fight was to cut off the ring and get Ali to the ropes so that he could hit Ali and try to knock him out, so since Ali was willingly lying on the ropes Foreman would plant himself in front of Ali and punch Ali as hard as he could. Foreman landed constant blows to the body, but had trouble landing punches to the head. Foreman began to tire from all the punches he threw at Ali to no effect, and with the punches he was taking from Ali, Foreman was visibly finished by the 5th round. Ali eventually knocked him out in the 8th round. Ali had regained the Heavyweight title with this strategy of lying on the ropes, and allowed one of the hardest punchers of all time to swing away at him.
In other words, avoid an election long enough for the polls to turn around and let the Tories punch themselves out.