Do party leader approval ratings predict election outcomes?

A significant amount of attention is given to opinion polls measuring the popularity of party leaders. The implication of much of this coverage is that the approval of party leaders matters when voters cast their votes. While photos of leaders struggling to eat sandwiches, or wearing inappropriate holiday attire, may make for good copy, what evidence is there to suggest that the popularity of party leaders is consequential for election outcomes? In this post, Jack Blumenau examines past trends in party leader approval, putting recent figures into historical context. He shows that leader approval ratings are much more volatile than general election vote shares, and that focusing solely on party leader approval leads to overly pessimistic predictions for the largest parties, and particularly for Labour.