I don't much accept that it has been a "concerted attack" as much as it is a fascination with the sensationalist. Of course it hasn't worked, becuase a lot of the support is akin to (not my metaphor) an 11 year old revelling in a new swearword they've found.
All it adds to is the sense of an establishment touted alternative to the establishment, a systemic siphoning of dissent into politics that are no threat to the establishment at all. The left opponenents can get sucked into a similar trap, but are more effective when outlining actual policy that is reactionary and anti working class. Such an approach tends to get less MSM coverage, for obvious systemic reasons (they support such policy and wouldn't present it as "bad").
The general nature of the current hype around the Euros was entirely predictable, though the scale has surprised even me.
But I don't think they'll hold 15% in the generals. 5 to 10 would be my pitch, probably the low end of that. The hype will die down somewhat, the "vote UKIP get Milliband" message will have some effect.
But most of all, I hope people continue to raise the anti working class, anti women and other absolutely demonstrable negatives of the party, along with the sense of general fraud and hoax.
After all, they did very well in the last Euros. What astonishing earthquake has there been in the establishment as a consequence? We have a tory government that is systemically corrupt and consistently gets away with it. Wow, that showed 'em.