So we ought to do all we can to make that off-chance a little bit bigger by voting intelligently. In order to do that, we need information. The first thing that intelligent voters need to know is which constituency they live in.
As Sarah Maitland's chronicles in our pages have revealed, this might not be as easy as it looks, even for politically-aware writers with degrees. (Imagine her disappointment when the answer turned out to be Kettering, and her MP Roger Freeman, one of the safest seats and one of the least enticing members of the Cabinet.)
The confusion is increased this time because most constituency boundaries have changed, and many of the names. But the electoral administrator's office at the local council will know. Or, if you are Internet-capable, you can enter your postcode at www.ge97.com and it will tell you.
Or you can wait until the week before polling day because it will be on your polling card.
Next, intelligent tactical voters have to assess the probable state of the parties in their constituencies. This means finding out how the parties would have fared if the new boundaries had been in place at the last election - and of course taking into account the significant shifts in public opinion since then, together with any special factors such as by-elections.
Inevitably, this involves making judgements about the validity of opinion polls and what other voters might get up to.
As a service to our readers, we offer this simplified guide
Tactical voting is not the same as single-issue voting, however, and people who want to vote for or against Europe, or abortion, or sleaze, will have to make their own way.
One seat which does not appear in the lists is Inverness, Nairn and Lochaber, the wide-open four-way seat left vacant by the retirement of Sir Russell Johnston, the Liberal Democrat MP.
According to the number-crunchers, the Lib Dems would have been ahead at the last election with 12,000 votes, followed by the Scottish National Party and the Conservatives, with Labour fourth, just 1,500 votes behind. Here, the layers of tactical calculation become too complex, so just vote for the best candidate.
Finally, the intelligent voter should check the lists of candidates when they are published after close of nominations on Wednesday 16 April to decide if there are really good reasons for voting for or against any of them.
Even anti-Tory tactical voters in Grantham and Stamford, for example, should pause before casting aside Quentin Davies, pro-European, hero of the Scott Report and hounder of David Willetts, the whip who tried to fix the sleaze inquiry. And what about the fiercely-principled Richard Shepherd in Aldridge-Brownhills, an honourable Euro-sceptic? Or Edwina Currie, fighter against petty-scepticism and for gay rights, in Derbyshire South? And even Sir Edward Heath, who agrees with all Tony Blair's policies, in Old Bexley and Sidcup?
If you want the Tories out...
The first block lists seats where the Lib Dems are best-placed to challenge the Tories. The second block shows where Labour lies a close third behind the Lib Dems, in which case you have to decide whether Labour's national advance will sweep them from third place. Elsewhere, anti-Tory tacticians should vote Labour in the list of Tory seats vulnerable to Labour shown on the swingometer on pages 6-7.
Vote Lib Dem
Brecon & Radnorshire
Isle of Wight
Devon W & Torridge
Somerton & Frome
Oxford W & Abingdon
Tweeddale, Ettrick & L'dale
Aberdeen W & K'cardine
Dorset Mid & Poole N
Hastings & Rye
Vote Labour or Lib Dem
Oldham E & Saddleworth
Falmouth & Camborne
Galloway and U Nithsdale
Vote Labour in the rest of Labour's target seats
If you want to keep Labour out...
Vote Lib Dem
Greenwich & Woolwich
Vote SNP Aberdeen N
Vote Plaid Cymru Carmarthen E & Dinefwr
Vote Tory Vote Tory in the rest of the Tories' target seatsReuse content