This chart shows historical voting intentions in the U.K. from the three main parties since August 1970. Data are from Pippa Norris’s website until August 1970 and the UK Polling Report thereafter, and are the answer to the question “If there were a General Election tomorrow who would you vote for?” [or similar]. Letter markers on the bottom show General Elections; number markers on the parties’ lines show other politically relevant events.

A few things to note regarding the data and its visualisation:

Duplicates have been removed from days with more than a single poll. This was a hatchet approach in Excel and removed some 600 results, mostly around elections and in the last five years.

The orange line shows the combined efforts of the Liberal Party (from August 1970), the Liberal Party and the Social Democratic Party (March 1981 to March 1988), and from March 1998 the Liberal Democrats.

At full zoom the data for each party are its mean for the month, as you move closer it shows weekly values, and zoomed in closer than ~8 years it shows individual polling results.

I’ve not included which pollster the individual results come from. It’s in the file but as yet not uploaded.

The data can be downloaded from this link.

You can’t zoom closer than 6 months, which might cause the Zoom button to act a little strangely.

I’ll add in more interesting points when I have more time! (You can make suggestions here.)

This was my first attempt at using JQuery (and my first use of JavaScript in ~8 years), it’s pretty good! Most of the legwork is done by the Highstock JavaScript library, which is free for non-commerical use and rather nice.