The evidence that Ukip are learning how to win at street fighting gives the main parties two big reasons to worry. First, it is clear from the Ashcroft polling that, where they fight hard, Ukip can hurt either party's local prospects. In both Thurrock and Great Yarmouth, Ukip's local momentum is hurting Labour – who are underperforming in both seats and could lose two otherwise strong pickup opportunities to Farage's party. In Thanet South, though, it is the Conservatives who are suffering – a seat which in normal circumstances would be out of reach could fall to Ukip or even to Labour. Secondly, arguments like "vote Nigel, get Ed" or "Vote Nigel, get Dave" simply won't work in seats where Ukip are ahead or in the fight. Voters presented with this argument on the doorstep will simply reply: "No, I've seen the polling. Round here it is vote Nigel, get Nigel."