So, here's the thing about lies.

If I start shouting to millions of people that you've been beating your wife, there's literally nothing you can say to undo this damage.

If you deny it, you'll just bring further attention to the lie.

If you ignore it, I'll keep bringing further attention to the lie.

Politics only works well when everyone follows some basic decorum.

They did, repeatedly, at the time.

And the scurrilousness of the leaflet was pointed out, too.

But xenophobia sells.

It was the pointing out which was the problem, as it brought prominence to the lie. There were plenty of other lies too, the one about NHS funding was especially egregious.