2013 local elections: Votes cast in the sorts of places where general elections are decided are the most accurate indicator of party prospects in 2015

The commonly used yardsticks of how well the national parties are doing in local elections can be confusing or deliberately misleading, and there is likely to be a lot of ‘spin’ after the elections of Thursday 2 May. Lewis Baston argues that studying the votes cast in marginal parliamentary constituencies, particularly in areas where there have been other local elections since 2010, is a better guide to electoral trends than council control, seats won, or even – sometimes – aggregate votes cast