We were always going to get a flurry of MPs announcing they were standing down at the next election. What’s surprising is that it’s happening so late in the life of this parliament.

Mark Simmonds is the latest to go, and though there doesn’t appear to be any subtext to his departure (he’s been pretty open about his reasons), the timing is unfortunate. There’s an impression at the moment of MPs jumping ship at the rate of almost one a week. David Cameron’s reshuffle in July revealed William Hague, David Willetts and Andrew Lansley were all bowing out. David Ruffley, Dan Byles, Mike Weatherley and James Clappison are among the Tory backbenchers to have joined them over the past month. And it’s not just the government: in recent weeks we’ve had Labour’s Frank Dobson, David Blunkett and Austin Mitchell all say they are off in 2015, likewise the Lib Dems’ Ian Swales.

It feels like Westminster has experienced a sudden spasm of anxiety about just how difficult things may become after the next election – more coalitions, more austerity – and a phalanx of MPs, both old and young, have all decided: I just can’t face it.

Voters will form their own conclusions about this behaviour. I’m sure the party leaders have done likewise, and may well be similarly unsympathetic. It’s one thing to announce you’re stepping down 18 months or two years ahead of polling day. But we’re less than nine months from the election, and less than eight months from the official start of the campaign. I imagine a few local party executives are discreetly despairing at seeing their summer holiday plans unravel. They’ll be well aware that each day without a parliamentary candidate is one less opportunity for door-knocking, garden fete-opening and – most important of all – getting a mention in the local paper.

Mark Simmonds’ departure touches on another factor that will have been swirling around the minds of restless Commons members: the Ukip narrative. Every time an MP, particularly a Tory in an English shire seat (which is most of them), announces they are off, Ukip gets namechecked – usually by the media, but sometimes, as in the case of Simmonds, by the MPs’ local party itself.

Ukip understandably loves and encourages this, regardless of whether it could mount a credible challenge or not. Simmonds won a sturdy majority of 12,426 in Boston & Skegness in 2010:

Since then Ukip have done well at the 2013 local elections for Lincolnshire county council, and again in the 2014 European elections, where they won 52% of the vote in the borough of Boston (their highest share of the vote in the whole of the UK).

As I’ve said before, however, you can’t extrapolate similar outcomes from different kinds of contests. It helps Ukip to have people talk about them in connection with parliamentary seats like these, but it also hurts them when expectations are simultaneously raised to the level of “being all over” their Tory opponent.

A perception of what Ukip might do, as opposed to what they can and actually will do, is increasingly shaping the story of this campaign. It’s a narrative that is becoming muddled with that of MPs scrambling for the exit, all of which just dilutes the important of politics in general and of polling day in particular.

MPs should relish the chance to take on all comers at the ballot box – not contribute to an impression of bailing out in an ‘early doors’ election.