Quote ="DaveO"Reminds me of when the SDP split the Labour vote and gave the Tories a large majority. I remember looking at the results in the papers and numerous constituencies the combined Labour + SDP vote was significantly higher than the Tory vote but the Tory got in because of first past the post.
Come general election time I don't think UKIP will do as much damage to the Tory vote as the SDP did to the Labour vote. I think a lot of Tories who might vote UKIP in a by-election will return to the fold if it becomes obvious voting for UKIP will get Labour elected. The UKIP vote might send a few marginals Labour's way but I don't think we will be seeing any safe Tory seats going to Labour in the same way the SDP vote gave strong Labour seats to the Tories.'"
Yes the rise of the SDP and the splitting of the vote was a far more significant factor in Thatcher's landslide successes of the 1980s, than the 'Falkands Factor' that is often brought up. In 1979 Thatcher won a majority of 43 with 43.9% of the popular vote. In 1983 she won a majority of 144 despite the Tory share of the vote falling to 42.4% of the vote. The big difference was the SDP-Liberal Alliance polled 25.4% of the vote, only a couple of percent behind Labour on 27.6%. Considering the Liberals in 1979 (before the SDP had formed and joined them) had only 13.8%, whilst Labour had 36.9%, it looks like around 9% of the electorate got displaced from Labour to the SDP.
The big difference between the SDP then, and UKIP now, is the SDP were displacing Labour from the centre (where the electorate is more densely concentrated) and UKIP are displacing the Tory vote from the right. So whilst UKIP will harm the Tories, they don't have as big a chunk to eat away.
The party that really displaced the Tory vote from the centre was New Labour under Tony Blair because he looked and talked like a centrist Tory and he was quite admired by the centre right business community, hence he had the Tories floundering under Major, Hague and Ian Duncan Smith. Whatever you think of Blair and I know a lot on the left distrusted him from the start, he was Kryptonite for the Tories.