Election 2005: What can happen?
This page first posted 1 May 2005
Current opinion polls show a Labour lead of 7% with a predicted
majority of 140 (as at 1 May 2005).
|Scenario||CON||LAB||LIB|| Lab Maj|
Is this outcome certain
to occur, or can other factors change the result?
As in previous elections (see 2001 errors)
the main sources of error in this result are:
The last of these introduces an error in the majority of about 20, and it is worth
remembering that all predictions are subject to that uncertainty. Given that, we
can explore the first two sources of error quantitatively to see if Labour is
certain to win on 5 May.
- Poll error - the opinion polls may not be accurate
- Tactical voting - voters in marginal constituencies may behave differently
- Model error - local factors and model approximations cause prediction errors
The pollsters' record in 2001 was not flawless. Although they correctly predicted
a strong Labour lead in the polls, they overstated the size of the lead by 6.5%.
Although pollsters have learned from the experience, no-one can be sure what the
polling error will be this year. Divisions of opinion are also apparent, for instance:
Considering a scenario under which the pollsters are again wrong by 6%, the actual result
- MORI favour restricting attention to those "absolutely certain to vote", which
reduces Labour's lead by about 4%.
- YouGov use internet polling, which they believe is more accurate, and which
reduces Labour's lead by about 5%.
|Baseline plus 6% pollster error||34.5%||35.4%||22.0%||52|
So Labour's parliamentary majority would be cut to 52, but they would still be comfortably able to
form a government.
In two-way marginal seats, those who naturally support the third-place candidate are crucial.
If they choose to support (or desert) one of the other candidates, the result can be affected.
In previous elections there was noticeable anti-Conservative tactical voting. In 2005, organised
tactical voting has been more diverse with different groups promoting anti-Blair, anti-Conservative
and anti-Iraq War tactical voting. However most two-way marginal seats are contests between Conservative
and Labour where the two leading candidates are likely to be pro-Blair, pro-Conservative, and/or
pro-Iraq War. In such seats, the most likely outcome is for "tactical unwind" where LibDem
supporters who voted Labour tactically in 2001 go back to voting Liberal Democrat, even though
their candidate is unlikely to win. With some irony, this is actually non-tactical voting as it
based on principle and protest rather than shrewd calculation.
The second largest category of two-way marginals is those between the Conservatives and Liberal
Democrats, where classical tactical voting by Labour supporters may be expected to operate as usual.
We assume a tactical voting scenario where there is
The outcome of this scenario is:
- Tactical unwind of 2% away from Labour to the LibDems in Conservative-Labour marginals
- Tactical voting of 2% from Labour to the LibDems in Conservative-LibDem marginals
|Baseline plus tactical voting||31.5%|
Even with tactical voting against Labour, it still would enjoy a landslide majority of 126.
Pushing the boundaries of the possible, we could ask what would be the effect
of both large-scale pollster error and anti-Labour tactical voting. This would
be a very worst-case scenario for Labour and an extreme best-case scenario for
the Conservatives. The result would be:
|Baseline plus 6% pollster error|
plus tactical voting
Even in this extreme case, Labour still has a slender majority of 16 seats in parliament.
What the people say
Pollsters: Different pollsters use different methods and ask different questions. For the record, here are their most
recent polls translated into seats:
|Pollster||Sample dates|| CON || LAB || LIB || Lab Maj|
|NOP||22-24 April 2005 ||30%||40%||21%||158|
|Populus||25-28 April 2005 ||31%||40%||21%||156|
|ICM||27-29 April 2005||31%||39%||22%||146|
|CommRes ||23-28 April 2005||31%||39%||23%||144|
|YouGov||28-30 April 2005||33%||36%||23%||96|
|MORI||28-29 April 2005||33%||36%||22%||96|
Markets: We can also get information from the financial markets as to the likely result. For instance,
IG Index makes a market in the Labour majority
which is currently trading at 74 - 80 seats (as at 1 May 2005). We can use our seat predictor in reverse to imply
party support figures from the majority. These are illustrative figures, and are not market
prices for party support.
|Pollster||CON||LAB||LIB|| Lab Maj|
|IG Index spread market ||34.7%||36.5%||22.0%||76|
The market is clearly a little more cautious than the pollsters about Labour's lead, but still predicts
a sizable majority of 77 (mid price).
Users: Users of the Electoral Calculus "make your own prediction" feature have been voting
anonymously by choosing their own scenarios over the past couple of days. The average results of over 5,000
separate predicted scenarios are:
|Scenario||CON||LAB||LIB|| Lab Maj|
|User-defined predictions ||33.8%||35.1%||23.9%||66|
This is definitely not a scientific survey of opinion, or even a survey of what people think is likely to
happen, but only an average of the scenarios that some people think are interesting. Intriguingly, the
result is closer to the implied market support levels than to current opinion polls.
Electoral Calculus users have also given their average preferred tactical voting scenario:
||TV CON||TV LAB||TV LIB|| Lab Maj|
|User-defined predictions |
plus tactical voting
||+2.4% to Lib||+4.8% to Lib||-0.8% to Lab
Users are predicting a modest amount of anti-Labour and anti-Conservative tactical voting
which takes 9 seats away from Labour, leaving them with a majority of just 48.
From a baseline majority of 140, there are many plausible scenarios under which Labour has
a much smaller majority. But almost every situation gives Labour at least a workable
majority and, in many cases, another landslide. Only the particular combination of serious
pollster error coupled with significant tactical voting against Labour shrinks their majority
to a small fraction of its current size of 160.
At current poll levels, there are no plausible scenarios which give either a
Conservative or a Liberal Democrat majority in parliament.
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