There is usually a protest vote at by-elections, and Ukip has been described as a pressure group, the sort that gets more votes at by-elections causing ripples in the community and making main parties stand up and take notice.
However, last week in Essex, the pressure group made an MP!
Is it a one-off? What happens if it is not a one-off? That is the more interesting question.
At the 2010 election no one party received an overall majority and we have a coalition. If Ukip get more MPs next May, the other parties will have to have less MPs themselves, so we might as well consign ourselves to being in a permanent coalition politically from now on, which means that all future decisions will be made by on a committee basis, and we know where that gets us!