The notion of core political values has long been of central importance in understanding how citizens evaluate policies, parties and candidates. However, the characterisation of these higher order values as, if not immutable then highly stable, has meant little attention has been paid to the causes and consequences of shorter term fluctuations. This paper demonstrates that switching allegiance between main parties led to significant shifts in the left-right political value dimension amongst the British public during the early 1990s. I use a True Intra-individual Change (TIC) structural equation model (Steyer, Eid and Schwenkmezger 1997; Steyer, Partchev and Shanahan 2000; Steyer and Krambeer 2003) on data from the British Election Panel Survey to examine the influence of party allegiance and changes in party allegiance, on change in the left-right political values of individual voters between 1992 and 1997. Results indicate that switching allegiance from the Conservative to the Labour party between 1992 and 1994 resulted in significant and enduring shifts in left-right values in the direction of the party of defection. Some change was observed between 1992 and 1996 for those defecting from the Conservatives to the Liberal Democrats, though this group had returned to their 1992 positions by the time they were re-surveyed in 1997. Those who stuck with the Conservative Party between 1992 and 1994 had moved significantly to the right by 1996, a position they retained up to the General Election in 1997. No change was observed amongst stable Labour and Liberal Democrat voters. While the absolute magnitudes of these value shifts were not large, the fact that left-right position has itself such an over-riding influence on party popularity, means that even small shifts in this value dimension can have sizeable impacts on the popularity ratings and vote share of the main parties.