The announcement by Dudley South MP Chris Kelly that he will stand down at the general election makes him the ninth Conservative MP elected in 2010 to choose not to recontest his seat.

This strikingly high number spells trouble for the Tories in two ways. First, it suggests that a significant number are not confident of retaining their seats. All of the nine (Louise Mensch, who resigned hers in 2012, Jessica Lee, Aidan Burley, Mike Weatherley, Chris Kelly, Laurs Sandys, Lorraine Fullbrook, Dan Byles, Jonathan Evans) represent marginals targeted by Labour, with six in the top 42 of the party's hit list. Detailed polling by Lord Ashcroft and others has shown Labour performing disproportionately well in its target seats.

Second, the decision of so many from the 2010 intake to stand down will make it harder for the Tories to defend their marginals. First-time MPs traditionally benefit from a disproportionate incumbency bonus as they build their constituency profile and as they face less well-known opposition candidates, rather than sitting MPs (who enjoyed their own local profile).

Combined with the defection of Douglas Carswell to Ukip, which both reflects and reinforces the Farageiste threat, the drain of 2010ers is further evidence of why many are finding it ever harder to see how the Tories win the next election.