Mark headshotMark Gettleson is an elections and polling analyst, focusing on British and American politics. He writes for and ‘The Knowledge’ in The House magazine. He is also a Liberal Democrat councillor. Follow him on Twitter.

When considering
the effects of a possible meltdown in the Liberal Democrat vote on Conservative
prospects at the next election, it is crucial to consider the kinds of voters
sticking with Mr Clegg, as well as those moving away from his party in droves.

Nate Silver, the extraordinarily insightful elections analyst at the
New York Times, has coined the term ‘voter elasticity’ to describe the extent
to which people in swing states actually change their voting habits. Why, for
instance, is Obama neck-and-neck with Romney in both Wisconsin and North
Carolina, when in 2008 he won the former by 14% and the latter by 0.3%? Largely
because while North Carolinians are fairly set in their party loyalties
(inelastic black voters and liberal urbanites vs. rural white conservatives),
Wisconsinites are far more open to persuasion.

Such concepts
clearly have a part to play amid the shifting tectonic plates of a
post-Coalition electorate. Those people who have moved towards the Liberal
Democrats in recent elections are among the more disloyal in their voting
patterns.  They are influenced by
new political information and therefore the most likely to be pushed back into
their former voting patterns by something they disagree with.

The bulk of these
voters backed Labour in 1997 and 2001, but the 2003 invasion of Iraq saw them
begin to waver. In 2005 and 2010, specific issues around foreign policy,
tuition fees and civil liberties, combined with a cultural aversion to what
they saw as New Labour’s right-wing populism, pushed them towards the Liberal
Democrat column. This may sound like a pure question of left-right, and that
does have a key part to play, but equally important is that these people didn’t
just flirt with Mr Clegg, they actually went the whole hog.  But others resisted the temptation –
the second thoughts of whom in the last few days of the 2010 election were
almost certainly the main basis behind the Liberal Democrats vastly underperforming
their opinion poll share. These voters are the most incensed at what they see
as Nick Clegg’s betrayal over university fees and indeed the very fact of a
Coalition with the Conservatives itself. 
In the cold light of day, these voters are waking up to their illicit
liaison.  They will return to
Labour in droves.

Other Liberal
Democrat voters, however, will prove comparatively inelastic. They may be in
one of the constituencies of the Celtic fringe, which has sent an esoteric
Liberal to parliament, possibly with some time off, since 1868. Their father,
grandfather and great-grandfather before them may well have been Liberals. Much
as breaking this loyalty is far from impossible, as Glyn Davies proved
sensationally in Montgomeryshire in 2010, but these voters will prove far more

Linked in with this
is locality. Lord Ashcroft's research on Liberal Democrat voters and the
Coalition proved fairly conclusively that those who were won over by national
politics were the most likely to desert Clegg's party, while those impressed
with the local record of their Liberal Democrat MP are the most likely to
stick. It is for this very reason that many Liberal Democrats in such seats go
to great lengths to change the question from “which party do you want to win?”
to “who do you want as your next MP?” The two groups have a clear logic to
them; for the politically-driven, the basis of their support has likely been
undermined by the Coalition, while for the locally-driven, this is less
relevant, as the local activity that provides the basis of their support goes
on. It is for this reason, again, that the Liberal Democrats so feared the
disruption to incumbency brought about by potential boundary changes.

The consequences
for the Conservatives in this local-national split form two sides of the same
coin. First, where the Conservatives hope to overhaul a locally active
incumbent Liberal Democrat MP, their voters will prove harder to dislodge and
comparatively fewer of them are likely to shift towards Labour – there are also
many seats Mr Cameron will be hoping for gains, particularly in the West
Country, where Liberal loyalties going back generations will prove harder to
shift. Next year’s county council elections will be fascinating in this regard:
in Somerset, for instance, where the Liberal Democrats had a poor performance
in 2009 yet went on to win five of the county’s six MPs the following year,
Conservatives will be hoping a major shift of votes from the yellow to red
column paints the county a deeper blue.

More crucially for
Conservatives, where there is a third-placed Liberal Democrat vote in a seat
without significant local activity from that party, those votes will have
almost certainly been obtained through national political messages – and will
therefore be the most elastic. It is with these voters that an obvious
left-right split becomes important – more precisely a Labour vs Coalition one.
While Liberal Democrat voters who feel favourably towards the Coalition may
well stick with Mr Clegg rather than leap to the defence of their incumbent
Conservative, those who find the idea of going into bed with the Tories
revolting will switch directly to Labour. 
In such a way, the Coalition has united the centre-Left and split the
centre-Right for the first time in a century. It should come as no surprise
that the first Corby by-election poll sees exactly this phenomenon, with more
than half the Liberal Democrat gravitating towards the Labour column.

This pattern will
likely repeat itself across Conservative marginals facing a tough battle with
Labour in 2015. By definition, it will prove particularly important where the
Liberal Democrat vote is large, where its growth clearly came at the expense of
the Labour Party in previous contests and, above all, where there are enough of
these defectors to overhaul the Conservatives. In total, there are 33
constituencies where the size of the Conservative majority is less than the
number of voters who moved from Labour to the Liberal Democrats since 1997
(estimated at the lesser of the number of voters Labour lost or the number the
Liberal Democrats gained).

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noticeable on this list are seats like Warrington South and Northampton North
where the Liberal Democrats as well as the Conservatives targeted the seat and
actions of both parties contributed to the Labour MP’s loss. In such three-way
battles, there is a far greater pool of disillusioned Liberal Democrat voters
on which Mr Miliband’s party will be able to draw. The Conservatives can
essentially kiss goodbye to many of these three-ways.

There are of course
a further 62 seats where the size of the Liberal Democrat vote in 2010 was more
than the Conservative majority over Labour. In such places, local factors and
demographics will unquestionably play a key part.

This is not to
mention the fact that there are a large handful of seats where national factors
intermingled with local campaigning allowed the Liberal Democrats to gain seats
off Labour in 2005 and 2010. With only a few exceptions, these seats can be
expected to return to the red column, taking Ed Milliband a few steps closer to
Number 10. As a final nail in this psephological coffin, the briefest glance
down the list of seats the Conservatives can hope to win off Labour in 2015
reveals a high number of metropolitan areas (such as Hampstead & Kilburn or
Bolton West) where the Labour incumbent will be able to benefit
disproportionately from the Liberal Democrat collapse. Don’t anyone mention a
possible rise of UKIP.

No Conservative
should underestimate the immense effects that a post-Coalition collapse in the
Liberal Democrat vote could play on their party’s fortunes in 2015.