I’m an unusual voter. I’m not a Liberal Democrat, yet I think Nick Clegg has been rather impressive in his two years as deputy Prime Minister.

Faced with the awkward arithmetic of the last general election result, he has ensured that Britain could navigate the world’s financial storm with a stable government. Despite his MPs being outnumbered by Tory MPs by more than five-to-one, he has secured some important policy victories, such as raising millions of low-paid people out of tax. Yes, he messed up over student fees; but his mistake was not so much supporting their increase in government: it was his bonkers pre-election pledge to abolish them. He must have entered coalition knowing that many Lib Dem voters would peel away: but, bravely and unusually for a major politician, he has put country before party.

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I say this to show that I bear no personal animosity when I say that Clegg and his party are in even deeper trouble than the headline numbers suggest. We know that they have lost more than half their general election support, and that Clegg has the worst ratings of the three main party leaders. We know that they have been hammered in local elections, and humiliated in the London mayoral contest and parliamentary by-elections. But look under the bonnet of our recent polls for the Sun and Sunday Times, and we find their plight is even worse:

Only 23% of those who voted Lib Dem in 2010 think Clegg is doing well as party leader. As many as one in three of the die-hards – those who have stayed loyal to the party – think he is doing badly.

Almost one in three of the die-hards now oppose the Conservative-Lib Dem coalition. Among all voters, the proportion of Lib Dem-voting coalition supporters who would vote Lib Dem is now just 6%.

Until recently, most Lib Dem loyalists favoured a continuation of a Conservative-led government after the next election. Now they are evenly divided between Tories and Labour. Among those who voted Lib Dem in 2010, a clear majority now wants a Labour-led government after the next election.

Given these figures, what should Clegg do, should he turn his mind from running the country to saving his party?

His first imperative must be to stop the boundary changes that he agreed to in the 2010 coalition government. The idea is to reduce the number of MPs from 650 to 600. My YouGov colleague, Anthony Wells, estimates that if the 2010 contest were rerun on the new boundaries, the Lib Dems would have suffered most, proportionately: they would have lost 20% of their seats, while Labour would have lost 11% and the Tories just 3%.

The nightmare of the boundary changes could be even nastier. Historically, Lib Dem MPs have often built up personal followings that have helped to insulate them from adverse national trends. But this insulation requires reasonably stable boundaries. If a Lib Dem MP finds that thousands of her voters have been allocated to a different seat, while she has acquired thousands of new voters who have never regarded her as ‘their’ MP, then personal loyalty will count for less.

In short the Lib Dems face a double whammy if the boundary changes go through. They will start the next election from a lower base – and their national unpopularity is likely to cost them more seats than if their MPs’ boundaries remained the same.

Lib Dem MPs are acutely aware of this. That is why some are saying that if they cannot make their dream of House of Lords reform come true, because of Tory resistance, then they will retaliate by blocking the boundary changes.

Their problem is that, though both reforms were promised in the coalition agreement two years ago, they weren’t linked. What was linked was the boundary changes to last year’s referendum on the Alternative Vote. The two commitments did not just appear in the same paragraph: they appeared in the same sentence. The Conservatives have a strong case when they say that they didn’t want the referendum but kept to their promise to hold one, so now it is the Lib Dems’ turn to keep their promise to cut the size of the House of Commons. (The referendum, of course, produced a large majority against changing our voting system – but the Tories never promised to back AV, merely to give voters a chance to decide the matter.)

So, to minimise their loss of seats at the next election, the Lib Dems risk the accusation of bad faith. And who could blame their opponents, to both their left and right, for reminding voters of the student fees fiasco and asking: how much is a Lib Dem promise worth? However, that this is a risk the Lib Dems will have to take.

The other big risk concerns a dilemma they can’t escape: whether to remain full coalition partners of the Conservatives right up to the next general election, with Clegg staying deputy PM to the very end, or to pull out a few months early and re-establish their independence. If they pull out, the aim would be not to bring down a minority Conservative government but to re build their own support. They would ensure David Cameron’s survival as Prime Minister, perhaps by abstaining on key votes, as they did last week over the calls for an inquiry into the actions of Jeremy Hunt, the Culture Secretary.

The polling evidence suggests they must give themselves time to reassert their independence. In order to recover at least some of the votes they have lost since 2010, they must persuade voters that, depending on the precise arithmetic of the next election result, they might well work with Labour in the event of another hung parliament.

However, I don’t think pulling out of the coalition in advance will be enough. If they fight the next election with Clegg as their leader, I can’t see many anti-Tories who voted Lib Dem last time returning to the fold. They will need a new leader whom voters regard as more even-handed.

That is why, for all my admiration of Nick Clegg, I suspect that his future beyond 2015 will lie outside government, outside the Lib Dem leadership and very possibly outside British politics altogether.

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