David Davis' 42 day Haltemprice and Howden by-election
David Davis' decision is not unique.
There is a long track record of people resigning their own seats to fight by-elections. There used to be such a tradition when people were appointed as cabinet ministers.
In 1912 George Lansbury was Labour MP for Bow and Bromley and a strong supporter of votes for women. When the Labour Party gave lukewarm support, Lansbury resigned to seek re-election with a clear mandate on the single issue. The Conservatives fought the seat hard and won. However in that case there was a Liberal government. The Liberals deliberately decided not to stand but did not endorse Lansbury either. Lansbury was beaten by a Mr Blair. Although Lansbury lost in 1918 he won the seat again at every election from 1922 until his death in 1940.
In 1938 The Duchess of Atholl, who had resigned the Conserative whip earlier in the Parliament, resigned Kinross and Western Perthshire to fight a by-election in opposition to appeasement but lost the seat to the new Conservative candidate.
1955 - Sir Richard Acland in Gravesend resigned in protest over Labour's support for nuclear defence to fight as an independent but the general election overtook events and the Conservatives gained the seat
In 1973 - Dick Taverne was deselected by Labour and fought essentially as a "Democratic Labour" independent and held his seat. He had no Liberal Candidate against him.
In 1982 - Bruce Douglas-Mann in Mitcham & Morden resigned on changing from Labour to SDP. The tories won because this was after the Falklands war. My feeling is had he done this immediately he would have won and the delay (persuaded by his colleagues - who did not do the same) caused the loss.
In 1986 15 Unionist MPs resigned to fight the Anglo-Irish agreement. Although they had generally little opposition the SDLP did make one gain against them.
(hat tip to various people on vote-2007.)
I am surprised at Labour bottling this. However, it appears that Kelvin Mackenzie may put up against him.http://news.bbc.co.uk/1/hi/uk_politics/7452117.stm
Note that Nick Robinson says "This resignation is quite extraordinary and without precedent that I can think of in British politics and means that politics is now utterly unpredictable." hmmm