Issues & Ideas | 8th October 2014

Not a single sitting MP won a majority of their constituency

Are some MPs more legitimate than others? Last week we took at by-election results since […]

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Are some MPs more legitimate than others? Last week we took at by-election results since 2010, and showed how eight Labour MPs have been elected by less than a fifth of their electorate.

While turnout is often low at by-elections, George Galloway garnered far more support in his by-election than these Labour MPs: he won nearly 30 per cent of Bradford West’s eligible voters.

But he still didn’t manage to convince even a third of his electorate. How common is this? Compared to the percentage of the vote MPs won in 2010, the 28.4 per cent Galloway managed is a fairly average sum.

There are 650 MPs. If we rank them all by this measure of legitimacy, the median MP won 30.1 per cent of their votes, which is very similar to the mean winning margin (30.6 per cent).

14 sitting MPs were backed by less than a fifth of their constituents.

In other words, most MPs are endorsed by less a third of their constituency.

At one end of the scale, six MPs won less than a fifth of their seat in 2010. Three were Northern Irish MPs (DUP), and the three others were Phil Woolas in Oldham & Saddleworth, Simon Wright in Norwich South, and Austin Mitchell in Great Grimsby.

Woolas has since been replaced by Debbie Abrahams, who just managed to pass 20 per cent, which leaves Wright, Mitchell and the three DUP MPs – along with the eight new Labour MPs elected in recent by-elections, and Mike Thornton, who held Eastleigh for the Lib Dems earlier this year – as the most illegitimate members of the House.

Who, then, is the most legitimate? Fittingly, it is the supposed future of the Lib Dem party, Tim Farron, who has enjoyed a national spotlight this week. 46.1 per cent of his constituency, which is 99.2 per cent white, endorsed the man bookies are backing to succeed Nick Clegg as Lib Dem leader.

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Marked by Kendal, the rural Cumbrian seat of Westmorland & Lonsdale handed Tim Farron the largest mandate in the country in 2010.

But even Farron did not manage to win over a majority of his constituents. While he won 60.0 per cent of those who voted, only 76.9 per cent of those who could vote actually did, which leaves him on 46.2 per cent. Can Britain be a beacon of democracy when none of its representatives were endorsed by even half of their constituents?

Leaving legitimacy aside, the data highlights the great electoral challenge that the Conservatives face and Labour could win the next election on: differential turnout.

Conservative MPs are elected by more of their constituents. Tories were, on average, backed by 32.9 per cent of eligible voters in 2010, whereas Labour MPs only won 28.3 per cent. The size of the constituencies won by each party may be slightly different, but given the average constituency has around 70,000 voters, Tory MPs won about 3,000 more votes than Labour MPs in 2010.

Tory MPs won about 3,000 more votes than Labour MPs in 2010.

On the one hand, that makes them more legitimate. On the other it scarcely helps the party win overall power. The Tories effectively waste hundreds of thousands of voters because they are grouped in seats where the party are winning comfortably.

Of the 100 MPs backed by the the highest percentage of eligible voters in 2010, 77 were Conservatives. At the other end, 66 of the 100 MPs with the smallest mandates were Labour. Only 1 Labour MP – then-Prime Minister Gordon Brown – won more than 40 per cent of his seat.

This is why Labour win are favoured to win the most seats at the next general election. We have shown how the party has a 35-40 seat advantage thanks to this effect. That is how many more seats Labour win over the Conservatives if both parties win the same number of votes. You can explore this in greater depth using our interactive election day predictor.