Seventeen Liberal Democrat MPs – nearly one-third of Nick Clegg's parliamentary party – will be looking over their shoulders as Labour support recovers. Among those suddenly appearing vulnerable are the party's deputy leader, Simon Hughes, and Chris Huhne, the Energy and Climate Change Secretary.

If the threat to Liberal Democrat MPs comes from voters defecting to Labour, then the first bloc of MPs to be worried will be the 13 (of 57) whose constituencies have, in the last decade, been held by Labour. Four of these now have fairly large majorities and/or such a weak Tory vote that they can relax.

But in the other nine, the majorities are not large and the Tories can hold on to their own voters well, so the sitting Lib Dem appears precarious. They include Children’s Minister Sarah Teather in Brent Central and the Equalities Minister Lynne Featherstone in Hornsey and Wood Green. The others are Bradford East, Burnley, Dunbartonshire East, Manchester Withington, Birmingham Yardley, Norwich South and Redcar.

A further 11 seats historically have had a large Labour vote of over 20 per cent. These former supporters have generally voted tactically to “keep the Tories out”, resulting in a heavily eroded Labour vote and the return of a Lib Dem. Of these seats, three have such safe majorities that the MPs could, if they have the nerve, not worry.

But the other eight – including Mr Hughes and Mr Huhne – know that “keeping the Tories out” is no longer a message that will work. The other seats are Bath, Berwick, Brecon & Radnor, Colchester, Portsmouth South and Taunton.

There are therefore 17 (9 plus 8) MPs who will feel under pressure.

That in itself will not mean that MPs will turn their backs on the coalition, but unfortunately for Mr Clegg, some of these MPs will have only too regular reminders of their mortality in the form of elections.

Many Liberal Democrat MPs face what may seem like almost incessant elections. It is the misfortune of those who represent former Labour territory that just when they have got over one set of metropolitan or district council elections they will be fighting another. Nothing can be worse for an MP’s morale than trying to motivate himself/herself and their workers while forever losing votes and seats at local election level.

A further difficulty in quite a few of these same constituencies is that they contain large numbers of students (and professors). The educational elite, as many MPs of all parties will confirm, is notoriously voluble and effective in lobbying.

So if as a Lib Dem MP you inhabit a constituency with a formerly large Labour vote, regular elections and a university campus, the next five years are likely to be hell in a Con-Lib coalition. They may be the first to be flaky in relation to the coalition.

Rob Hayward is a psephologist and the former Conservative MP for Kingswood