A tale of two coalitions: using German opinion polls to predict the future

Guess who:

This party achieved its best election result in a generation recently. Then it went into coalition with the main Centre Right party, since when its support has collapsed.

It is, of course, the German Free Democrat Party, who achieved nearly 15% of the vote in the 2009 elections, and then formed a governing coalition with the Christian Democratic Union. Fifteen months on, one recent opinion poll showed the FDP polling at a mighty 3%.

The German elections took place seven and a half months before the UK elections, and both resulted in a similar outcome. So I wondered whether there were any other parallels in how public opinion in the two countries has changed since the elections.

To find out, I took monthly data from Forsa opinion polls in Germany and YouGov opinion polls in the UK. I compared the opinion polls results for each successive month after the election (so the first poll compared October 2009 in Germany with June 2010 in the UK, and the latest comparison was between May 2010 in Germant and January 2011 in the UK).

- After 8 months, the FDP in Germany had lost just over half their support from the election, going from 15% to 7%. At the same point, the Lib Dems had also lost just over half their support, from 24% to 10%.

- In contrast, support for the CDU and the Tories had stayed roughly the same as at the elections (CDU was down 2% after 8 months, the Tories were up 3% after 8 months). As a result, the governing parties lost 10% of their support in 8 months in Germany, and 11% in the UK over the same time period.

- Labour's level of support was almost exactly the same as the combined score for the SPD and the Greens at the same point after the election. After 8 months, combined support for SPD and Greens was 42%, for Labour was 41%. With the exception of one month, Labour's opinion poll rating has been within 2% of the combined SPD/Green score for every month since the election.

- Labour recovered support more rapidly than the SPD/Greens in Germany, gaining 12% in 8 months compared to 8% - possibly a result of more effective leadership and campaigning? However, they started from a worse position. In the 2009 election, the combined SPD/Green vote was 34%, 15% behind the CDU/FDP. In the 2010 election, Labour got 29%, which was 32% behind the combined Tory/Lib Dem score.

There are considerable differences between British and German politics (a Left Party which gets 10% of the vote in Germany, different electoral systems, different economic policies, leaders and much more). However, it is interesting to note these similarities in trends in opinion polls since the respective elections and formation of a Conservative-Liberal coalition. If these similarities persist over the next few months, we could expect the following:

1. At the local elections in May, the combined vote of the Coalition parties will be just 4% more than the Labour vote. Labour's share of the vote will peak at 46% during the summer.

2. The Lib Dems will continue to decline in support, and by next July or August will be at 5% in the polls. The Tories will continue to poll close to their score in the General Election over the next six months.

3. Other parties outside of the Big 3 or 4 will continue to get a similar share of the vote as they did at the General Election.