The theory behind it is that the MP who the lib dem defeated would have had a personal vote which is now lost and the new lib dem incumbent has time to build up a personal vote. Therefore in the second election of the sample (2001) in which the Lib Dem MP stands for they generally increase their share of the vote.

These seats have not been selected at random. They are all ones that the Lib Dems took from the Conservatives in 1997. Labour wasn’t exactly loosing seats at the time if you recall so it is solely Con-Lib Dem seats. The Lib Dem incumbent has remained continous throughout. In a few seats we have seen the Lib Dem MP change and I have excluded these seats  you can’t judge the effects of incumbency with a changing incumbent. I have also excluded Winchester because of the by election in 1997.

The national picture for the Lib Dems from 1997-2005 has been one of progress with an increased national share of the vote in both 2001 and 2005. Below are the seats with the size of the Lib Dem vote in 1997 and the percentage share.

For table see http://parburypolitica.wordpress.com/2007/10/24/the-trials-and-tribulations-of-a-lib-dem-incumbent/


Below are the same seats in 2001 as you can see from the swing column the average gain is just over 4% with 71% of the Lib Dem seats seeing their share of the vote increase.

For table see http://parburypolitica.wordpress.com/2007/10/24/the-trials-and-tribulations-of-a-lib-dem-incumbent/

Now here comes the important bit and remember this is at a time when the national picture for the Lib Dems is positive with an increased national share of the vote. What we see is that 61% of Lib Dem incumbents see their share of the vote fall. As time passes the law of diminishing returns effects the benefits of incumbency and after they have won two elections they think they can afford to get a bit complacent. Now the effect is not universal and is not massive but it is worth bearing in mind for close election contests against a Lib Dem opponent.

What we don’t know is whether the same  pattern will be followd in the seats that the Lib Dems took off Labour in 2005 but it doesn’t take a genius to work out that a Labour PPC is less of a challenge to a Lib Dem who has the benefits of incumbency rather than the reverse. Therefore it is important for the party to concentrate resources  in the seats they gained from us last time where in many cases we have a decent chance of retaking them.

For table see http://parburypolitica.wordpress.com/2007/10/24/the-trials-and-tribulations-of-a-lib-dem-incumbent/



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