Guest slot: RodCrosby’s by-election trend analysis

Guest slot: RodCrosby’s by-election trend analysis


    History shows the challenge facing the Tories

RodCrosby has done an analysis of by-elections swings, and the Swing-Back to governments’since the War.

Using the Butler swing between Labour and Conservative, the Swing-Back is defined as the difference between the average swing to the Opposition in by-elections and the swing to the Opposition at the subsequent General Election.

So, for example the average Butler swing from Labour to the Tories in by-elections 2001-2005 was 7.9%. The swing the Tories obtained in the General Election was 3.1%. Thus the Swing-Back to Labour in 2005 was 4.8%. For John Major’s last term the equivalent figures were 13.6% and 10.2% – a Swing-Back of 3.4% to the Tories.

The remarkable feature of this graph is that the Swing-Back to government has been highly consistent since at least 1974, irrespective of party in power, government term, parliament length, number of by-elections, turnout, and the relative strength of the Liberals in either by-elections or General Elections.

    It has ranged between 3% and 5% with a very stable average of almost exactly 4%. It thus has all the appearance of an “Iron Law.”

So, if we subtract 4% from the average by-election swing to the Tories by the end of this parliament, we might have an excellent prediction of the General Election swing to within plus or minus 1%.

In other words, it would seem that for the Tories to be on course for an overall majority – requiring a swing of about 7% at the next General Election – their by-election average swing would need to be of the order of 10%-12%, to allow for the historical expected 4% Swing-Back to Labour.

After Bromley (to be fair to the Tories we should ignore Blaenau), the average by-election swing currently stands at 3.9% – low by any standards.

The Swing-back rule implies that if Tony Blair went to the country tomorrow, we would expect – so far as the Labour and Tories are concerned – a near-exact re-run of 2005, within the range of a 1% swing either way. Depending on the boundaries and the operation of the electoral system, Labour would seem quite confident of a 4th term with the Tories not even competitive.

We are now into the second year of this parliament, and of course things may yet improve for the Tories.

    But, assuming this parliament runs to a full term, the Tories really need to be recording swings sometime, someplace in the range of 15-20%+ to bring their average up to a level where they seriously threaten Labour for power.

Failing which, despite all the understandable hype and interest in the current Tory leader, historical precedent unswervingly suggests that he will barely dent the Labour majority in 2009…..

RodCrosby is a regular contributor to PB.C discussions

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