This article is fascinating. Excerpt:
…it was the “switchers” who provided the most compelling evidence. By examining declared voting preferences for the period 1991 to 2004, Professor Oswald and Dr Powdthavee found that 539 people switched from Left to Right, and 802 switched from Right to Left. The most significant difference between these two groups of switchers? The voters who swung from Right to Left had borne, on average, more daughters.
Read about the cross-sectional results as well.