The Spen Valley by-election of 1919 was held on 20 December 1919. The by-election was held after the death of the incumbent Coalition Liberal MP, Thomas Whittaker. It was won by the Labour candidate, Tom Myers, who had contested the constituency at the 1918 general election.
1919 Spen Valley by-election
The poll came at the same time as a serious split in the Liberal Party over continuing support for the coalition government: Colonel B C Fairfax was nominated as the Coalition Liberal candidate, and Sir John Simon stood as an Independent Liberal. The poll was held on 20 December 1919, but the votes were not counted until 3 January 1920. The result was seen as sensational, with The Times describing it as a "political event of great significance", with voters deserting the government candidate in "a humiliation which cannot be explained away".
In the view of Maurice Cowling, Simon's defeat by Labour marked the point at which Labour began to be seen as a serious threat by the older parties.